Who has a twitter account they don't care about, even at sign-up? Probably millions of people.

Bots? Combines with the insane high number of mail.ru it would be my guess that mail.ru has made it easy to creates account in some automatic way and that's what the bots are using, along with a silly password.

You would be surprised how many people in India (and elsewhere, for that matter), have that as their online banking password.