In the next beta patch (coming soon), we'll be making some changes to the way we store character data. These changes won't be visible to players, but we'll need to wipe all characters in Diablo III beta in order to fully implement them. As with previous characters wipes, this wipe will also affect gold, achievements, followers, and artisans.
We're currently looking to release beta patch 8 before the weekend -- potentially as soon as this evening -- but we don't have a precise ETA. We apologize for the short notice and thank you for continued testing and feedback.
The changes we're making to the way we store character data won't be visible to players, since they're being made to the database, but there are also other changes going in with beta patch 8 that will be visible (and thus noted). I'll get those patch notes posted as soon as possible, but not before we actually start the patching process.