CrashPlan's horrible password reset security
blog.androgynoid.com
blog.androgynoid.com
If you use the 2 password method, your backup archive is then further protected by one that you cannot simply reset. If you forget this password, you might as well say goodby to you backups.
The last security method involves using your own keys. This is also not easily reset without destroying your backup archive.
There is at least some comfort knowing that even if the account is compromised, your data is still inaccessible...