Why do we like some Naruto pairing?
 
I'll try to explain this with some examples. Take NaruHina, some people say: "oww that's because they are so cute for each other and Hinata deserves him". I ask why? That's because NaruHina is just not only the way they look together but the way they complement each other too. They help the other to grow into a better person, we all know how Naruto has inspired her to follow her way of the ninja... and Hinata... well she's helped him in some kind of way, remember the scene before the Neji and Naruto match? she helped him to believe in himself and then she became the type of person Naruto likes. (For more of this read: Believe: Uzumaki Naruto/Hyuuga Hinata from x_darkhope_x and oniraitei posted at the LJ community ship_manifesto)
 
My point here: Both of them helped the other to grow up.
 
Let's take another pairing like NaruSaku. Sakura also got inspired from Naruto, after the infamous promise of a lifetime, she realized she musn't depend on Naruto all the time and after he left to train with Jiraiya, she asked Tsunade to train her and become a useful and skillful ninja. (Thoughts taken from Because I'm here - a Naruto/Sakura manifesto from heronite posted at the LJ community  ship_manifesto)
 
The conclusion? The same as before, they all turn into better persons (even Rock Lee inspired the pink haired kunoichi). That's the wonderful thing about the relationships in Naruto. The characters aren't so complex for nothing, they teach you a lot.

 
Why pair Neji and Ten Ten?
 
Actually that's a question I should ask other people. One of the reasons I've found it's because she's THE girl in his team and she admires him and blah blah blah. Seriously, do you really think she admires him that much to the point she wants to become a better kunoichi? I think that rol has already been taken by Tsunade.
From Neji's side, do you know any way in which Ten Ten has inspired Neji to grow? No? Well me neither. It was Naruto and with some help of Hinata that he changed for good.
And the 'she is THE girl in the team' reason... we'll discuss that later. I'll be adding more reasons as we move on.
 
What about one-sided shippings? 
 
Although I'm not quite sure if there's a difference from my previous examples, I'm answering this to be safe.
 
NaruHina has yet to have more development so I think it's safer to label it into the one-sided shippings. Along with NaruSaku, the one I'm not that sure if it's still one-sided, these two I've already made my point so let's move on into a new one.
 
SasuSaku is a popular pairing, and due to the uncertainty of Sasuke's feelings in part II I'm placing this ship into the one-sided ones. Sakura seems to really love him (even if it could be mistaken by a childhood crush) and Sasuke has once said she's an important person for him so the pairing is reasonable. We all know how little Sakura has matured through all the story and her little crush became trully love as the time passed. She was one of the few persons that knew his real self (remember that Sasuke didn't let her tell Naruto about his seal) the other one being Kakashi. It's funny how she, being the heroine didn't know Naruto that well (the main reason beeing that Naruto only showed his real self to Hinata before his match with Neji and maybe to Iruka when he was a little kid). So it's the same as before, people growing into better persons for the ones they love. And here's an extra thing, one of the persons involved have showed the other one a side of his that he never showed anyone else. So the relationship (in the safe sense) becomes more intimate. (For more info read. Blooming  from  zauberer_sirin  posted at the LJ community ship_manifesto) 

What if NejiTen is also one-sided?
 
We've already discussed the reasons why those two should be together for all the eternity so now let's see some proofs about this shipping (yeah I could be that sarcastic).
 
Does Neji love Ten Ten? (let me laugh at this first... hahahhahahahahha... ok I'm done) I think our stoic Neji even loves Lee more than he loves her (you know, boy-boy relationships in Naruto are really intense, most if they are in the same team).
 
I see Neji more of the Sasuke type, you know the cool character that despises the loser in his team but that deep inside cares about both of his teammates. He also has his own tragedy, been born into the branch family, and losing his father for the sake of the main branch, leaving him to hate them all. But he has other things that makes him different than Sasuke too. Neji hasn't showed his real self to any of his teammates and certainly Lee and Gai knew more of his tragedy than Ten Ten.
 
Also, even if he's that cool, he demonstrated during the chunnin exams that he trusted his teammates that much to the point of not worrying about them. He didn't look surprised nor worried when Ten Ten lost against Temari. A different effect produced Lee's lost against Gaara to him, though. Even if we could only read the I-told-you-Lee-a-dropout-remains-a-dropout thingy, you could notice he was concerned, a thing he didn't express with Ten Ten's loss. And finally, there's no the 'protect Ten Ten' thing inside Team Gai. Of course that makes her a reliable kunoichi but with that, there's no place for the 'protect precious people' nor the 'precious people' thing at all.
 
So the Neji's side was solved but Tenten? Does she even likes him a bit like Sakura likes Sasuke? (or Hinata likes Naruo for all that matters) The answer is NO, she doesn't even fangirl him. I mean, I know she hasn't had a development so far (and don't think she'd have one in the future) so why assume those things... When I saw them in anime at first I only saw two teammates helping each other, speaking about their training sessions of course, and we all know that's because Gai was busy with Lee (speaking about preferences). Let's face it, who better than your sensei to train you?
 
And what if Ten Ten's admiration towards Neji turns into love? Well, I'm sure you've all have seen the way she was looking at Lee while they trained... with that pervy smile. Surely she hasn't watched Neji the same way, so stay cannon people.
 
Why I dislike the pairing?
 
Although I admit at first it was some kind of fangirl jealousy, now I see it in a more 'scientific' way. People pair them 'just bacause', because she's the girl in his team? I think that's offensive for both characters... when you pair (use) them like that and don't have a proper reason to do that. But I think that's crack, KakaIru in there. That's all I have to say.