Blackberry won't lose too many customers that'll worry them just over that. They'll just find another medium to launch attacks.
They'll loose more then they think, them helping the police is going to make a lot of people switch over to iPhones as they are going to have iMessage or w/e that shit is called.
I have a blackberry and if I did live in London, jesus I would switch in a heart beat. I've talked about hacking on my blackberry before and stuff, But I live in Vancouver.