Ick... why give them all your files to index? Just get your own hosting account.
well, not that I'd run out and upload all my files to google but, I guess the arguments would be:
Cost (free google vs. paid hosting),
Performance,
Stability,
Security.
Yeah, I know that last one is going to cause a spark. But if you consider google "secure", than they can likely do more to protect your files than you can on a host where you don't even have root access.
Plus theres the whole social network aspect, where you can have public files to share.