It's all in how you do it. I know plenty of businesses that have gone nowhere but up buying good lists and emailing them in a personal-feeling manner (with clear unsubscribe instructions. It's not legally spam-- and if your audience isn't geeky, it's not generally going to piss them off.

I also once heard that the thing that made Art.com into a huge business was buying the pottery barn list, cross referencing it with new home buyers, and sending catalogs to the resulting list.

We've never done it-- but I don't think it's universally a bad business decision.