I just came across Rlweb's Bitcoin Generator, a Chrome extension that claims to be the "first google chrome extension creating Bitcoins".
This extension looks quite shady to me, they don't even have a link to their website. Is it a scam?
Would it at least in theory be possible to write a miner application as a browser extension?
With GPU support?
Edit: For completeness, I found another Chrome extension named Bitcoin Miner.
This one looks more legit, but it says it's a Flash game. It doesn't really generate bitcoins, or does it?