vBulletin used to have the ability to report on stuff like that, which was useful for allowing bespoke weak password warnings. Now, it only has an automated check of users with the same username and password. We have 34 of those currently.
Yes. How strong it is, I don't know. vBulletin is software for messageboards, not financial transactions. Even encrypted stuff can be cracked or brute forced if enough processing power can be harnessed.
Particularly if your safe gets compromised...
Mumsnet, the popular, parenting website has been hacked: http://www.mumsnet.com/Talk/site_stuff/2451970-Site-attacks-hackergate-and-resetting-passwords-heres-what-we-know-what-were-doing-about-it-and-what-we-think-you-should-do-PLEASE-READ-PART-TWO?pg=1
If you know anyone who uses the site, or...