Mmm, I got bored waiting for it to load, and I have broadband.
The only decent "online" adventure games I've seen were the Lozenge and Hampshire series, which were knocked up in DHTML and loaded straight away, even on a dodgy old modem. You could even save your game using cookies. According to my big pile o' bookmarks, they should be hiding here:
But of course, they're not. Alas.
Not the future
of adventure games, but an avenue that can work for fan-games and the like - just as long as they don't take five years to download and require you to update your Shockwave.