Super Smash Bros. for 3DS: There's No Need to Nerf Little Mac!
From a purely positive viewpoint, Little Mac is an unstoppable killing machine. A lot of his moves have super armor (which means he doesn't flinch) and are incredibly powerful. Eventually he gets a "KO punch" that will take an opponent down in a single blow, if he can land the move. He's a fan favorite for button-mashers and beginners, and I think that may be why people want to nerf (or depower) him.
Little Mac is extremely easy to use. He's accessible, which means that button-mashers can jam the A button and rack up damage, while beginners can do the same and destroy opponents that are not prepared for it. Mac is fast, and he can hit pretty hard despite being very light. So a lot of veteran players think he's overpowered. But being accessible and being overpowered are two different things. He may be overpowered in some aspects, but he does have his share of weaknesses, and thus doesn't deserve to be nerfed. Why?
Mac's Recovery Moves are Horrendous
Mac's recovery moves are horrendous. His up special barely goes up, while his side B is not much better. Paired with his weak air game and small double-jump, recovery is Mac's Achilles' heel. A smart player can easily get Mac off the stage and gimp his recovery (using really any move to hamper the recovery move). The best strategy is to stay near the edge, do whatever you can to get Mac off the stage, and gimp his recovery, killing him at low percentages. (Ike had ths same problem in Brawl, and really Mac is just a quicker Ike.)
Mac's hard-hitting attacks and beginner-friendly play style don't make him an overpowered character. He may only have a few weaknesses, but if you cannot take advantage of the few weaknesses a character has, then you are going to get the percentage beat out of you. It's simple.
There are many characters that might require nerfing in the future, but Little Mac is not one of them. Besides, does anyone really think that Nintendo will nerf a pretty well-balanced character, when they didn't do so with Metaknight in Brawl? I doubt it.