At this point, I've basically stopped answering my cell if I don't recognize the number. If it's important, they'll leave me a voicemail (it never is.).
One other thing I did was ported my landline over to callcentric.com, where for $3.50/month or so, I can 'firewall' all calls coming to that number, making it safe to give out to anyone. Their call treatments allow me to, by specific number or patterns (800*), drop, send to voicemail, play the "number disconnected" tone, forward, etc. It's great - no more calls I don't want.
One other thing I did was ported my landline over to callcentric.com, where for $3.50/month or so, I can 'firewall' all calls coming to that number, making it safe to give out to anyone. Their call treatments allow me to, by specific number or patterns (800*), drop, send to voicemail, play the "number disconnected" tone, forward, etc. It's great - no more calls I don't want.