The CAPTCHA's they use have been put through the ringer
and are proven to work against spammers who are focused
and resourceful.
Not really:- http://securitylabs.websense.com/content/Blogs/2919.aspx
- http://www.cs.sfu.ca/~mori/research/gimpy/
- http://www.zdnet.co.uk/news/security-management/2004/05/06/s...
- http://caca.zoy.org/wiki/PWNtcha
etc. Most of those articles are from several years ago. The state of the art has improved since then.