From the mouth of Todd Howard:
"We don't code in a maximum level. There is a theoretical maximum depending on what your skills are. The one change we've made is that you level faster. We've sort of balanced Oblivion and Fallout 3 in some respects to like a 1 - 35, 1 - 30, so if people play for a long time that's the kind of high level with creatures and whatever. This one is balanced like 1 - 50, but that isn't longer in gameplay. You do level faster, a lot faster, especially in the beginning of the game. Because of the power in the perks, we wanted to be giving them out at a higher rate. The actual maximum depending on your particular character how it works out might be 75. I don't really know. I'm just saying we don't code in the maximum level. It will end up whatever it ends up."
"(Perks being more fun) It's the thing you're always shooting for. Even 1 - 50 it slows down a lot as you play. If you assume there's 200 hours of content, you can sort of figure out, 'how often do I get to level?' We think we can balance that with the perks. That's what happened. We did the perks, and we figured out quickly, 'oh, to make these work, we need to be leveling faster.' And it is more fun."
And: "And I think the game right now has like 280 perks if you include the ranks. So even a character that raises all their skills to 100, and they're playing and they're level 50, they've only gotten to pick 50 perks."
This is where you're 50 max perk rumor came from. Now where does it say only 50 perks?