Last night when the Friends and Family Beta Patch 2 was released, all characters were wiped. No explanation was provided for the wipe. Some fans speculate external closed beta might start very soon, but the wipe might be unrelated. That has happened in past beta tests.
Bashiok: We’re in the process of bringing down the Diablo III test server to deploy a patch, and wipe all characters to continue the testing process. We anticipate the downtime to last until approximately 8:00 p.m. PDT. — source