Data losses in Snow Leopard bug

Users of the new Apple operating system Snow Leopard are experiencing massive data losses when logging into their machines under a guest account.
The problem appears to affect those who had a guest account enabled before upgrading to Snow Leopard.
Users have in some cases lost their entire main profile, including sites, pictures, videos and documents.
The problem, reported by more than 100 users on discussion forums, surfaced shortly after the OS's August release.
The issue follows closely on the heels of vast data losses by the Sidekick handset in the US, whose software was designed by Microsoft subsidiary Danger.

Unwelcome guest
Indications are that the Snow Leopard bug simply treats the principal account like a guest account - meaning that the account profile is wiped clean when logging out.