Here's why I think Kamek should be in Brawl:
Let's go back to 64. When the first smash came out, it was obvious that Mario was the main series. Mario, Luigi, DK, and Yoshi were all derived from the Mario series, and there were even rumors that Bowser and Peach were supposed to be in as well. Thus, a quarter of 64 was Mario based.
Move on to Melee. Peach and Bowser join the fray, along with the crapeo clone that was Dr. Mario. That's 5. Apparently, this was enough to push DK and Yoshi into their own reps from their own series. There were also many trophies from each's respective series.
Move onto Brawl. Mario at the moment only has 3 reps, which will (hoefully) be boosted to possibly 5 or 6, including Luigi, axing the Doc, and maybe adding Bowser Jr. or Toad. Now more than ever, DK and Yoshi are being considered loners in their respective groups, especially with the fact that it appears that Lucas, Cpt. Falcon, and Wario will remain loners. However, DK and Yoshi have been around since 64, and by now they each deserve at least one more rep. Some may even think two.
DK now has at least Diddy, and may get King K. Rool. Yoshi STILL has no one. Granted, there's only been 5 games in the Yoshi series, only of which two should count, but I believe the YI series is more than popular enough to warrant another rep. And there's only one really good cchoice: Kamek. The main rival of Yoshi, e could get a moveset made easilly, and be a glider with his broom. I believe he should be in Brawl, and he has good enough reasoning to.
Another factor is that Kirby was a loner, but now has three reps, and Earthbound MIGHT have two (pending on Ness's confirmation). F-Zero is more or less a moot poin, because it's probably the most "unpopular" of Nintendo's series.
Long story short, by now I believe that only new series being rep'ed in Brawl should be stand-alones (Warioware, Animal Crossing, Pikmin, etc.), and series that have been around a while (F-Zero excluded) should get another rep. DK did. Why can't Yoshi?