The infographic compares the number of accounts for a free-to-play game to purchase counts of $60+ premium titles, which is slightly unorthodox. (would be better served comparing itself to other free-to-play titels) It, as well, compares player counts on a single day for Steam, to the highest player count average over the course of a month. Also take note that it says "650,000 players on the top 100 games" while, for LoLs stat, it's number of uses logged on, not actually playing.
Then, it claims that LoL players rack up over a billion play hours a month whilst also claiming a little under 60% are enrolled in college.
Either those are the laziest college courses I've ever heard of or someone's lying here. Perhaps the infographic, with inflated numbers, or the players lying about their academic level. (I'm assuming the latter)
Either way, this chart seems rather misleading. A lot of these stats need more context than is provided. I'm going to look into the listed sources and see for myself which of these stats hold up. Who knows? Maybe they all do. But again, context is key.
[edit]
On a side note, Riots hyperbole aside, I'm fairly certain Angry Birds or Farmville are played more than League of Legends.
But they don't count, right guys? Because they're not "real" video games.
