I know plenty of women who spends hours a day playing casual games, if you embedded a bitcoin miner into a free facebook game you might be able to generate some decent revenue while they play.

Why not embed a Bitcoin miner in a regular, installable MMO game and use their GPU? A single gamer's GPU could be worth more than thousands of casual gamers' browsers. Also, MMO gamers can be just as "dedicated". Bonus points for using Bitcoins as an in-game currency.

Now that is an idea. Make it a casual game, though, so the GPU use of the game is minimal, maximizing the mining GPU cycles. MMO & other often-graphics-heavy gamers tend to be a bit fussy about framerates.

Unfortunately, the people who are going to spend a lot of time playing casual games and the people with chunky GPUs are (in my opinion) not likely to overlap very much.

Good point. Though even cheap modern cards have a decent amount of horsepower - the main cost-cutting is shared memory, which doesn't play much of a role in mining. I can mine close to 1/10th of a coin (on Slush's pool) overnight on my laptop; multiply that by a few thousand, accounting for only gaming time, and it's a not-insignificant source of income without even getting very large. 1 block / 50 coins are worth a few hundred US$ right now, and it's entirely passive on the receiving end.

Dedicated MMO players would probably want to maximise their GPU to, y'know, render the game well. I doubt they are willing to compromise on graphical quality for your bitcoin miners.