Yeah I remember 3D the first time around, quite clumsy iirc, people just weren't 'ready' for it back then. It's a relatively easy sell now because we're so technologically dependent these days, LCDs, TV, computers, consoles, PDAs, mobile phones, Pads, and all manner of 'interface' mechanisms. The headaches you mention do seem to be a legitimate concern from what I've been reading so it may just be a question of easing the brain into the medium slowly.
Regards adverts, in a word no because it's all about control, something you don't get when using services like Google Adwords and such like. Paid content downloads are certainly possible (mods etc), but there are a number of factors that would need to be looked into, including whether doing that would break the EULAs of the games being modded.