Wow.
I had trouble a few years ago as something using directly connected MIDI missed a mere few centiseconds (was a weird buffer issue) and it was noticed. I can't imagine the sort of latency a browser and connection (no matter what sort, you're up against laws of reality if pulling data from potentially the other side of the planet) would introduce.
But, then, people seem to accept dreadful quality videos where areas of similar colour (especially dark colours) end up as dancing blotches of the same colour, so maybe they'll accept horrible out of time music.... just call it post-dubstep or something, it'll be okay...