A small but understandably very upset group of people are reporting a bug in Snow Leopard that totally wipes out account data without warning. The consensus is that it has something to do with guest accounts: the data loss seems to come directly after using one, when trying to log back into a regular account.
Documentation on the problem is still thin, and Apple hasn't issued any kind of response, but until this gets sussed out, you should probably cut back on the guest logins, lest you lose everything you've ever saved to your Mac, ever. Any new operating system has bugs, but if real—and it's starting to look that way—this one is pretty atrocious.
We'll keep an eye on this, since the more exposure it gets, the more likely people are to come forward with their own personal horror stories. Post 'em if you got 'em, in the comments. [ITWire via Neowin]