Bouncing spam vs. Blackholing spam

[Marc Perkel]

I've been blocking a lot of spam at connect time that I am 100% sure is 
spam. However I'm wondering if that is the best idea because it gives 
spammers feedback as to what works and what doesn't. If I silently 
absorb the spam and let the spammers think it's delivered then they have 
no way to know if the spam is getting through or not.

Thoughts?