SO I say, go ahead and add them.
Chris... where have you been? We have had extensive discussions recently where we all concluded that we have to make getting the FPs down a priority and the only way to do this is to (gulp), allow some graymarketers loose (those who do a some or much spamming but who do have some legitimate uses). It wasn't an easy decision... but the need to get SURBL to a "set it and forget it" point is mission critical.
However I would like to see an example of a spam'd blog.
Happens all the time in the comments section of these blogs. Not often with blogger.com, more often with Moveable Type blogs because (1) these link to the comments section, (2) the comments section is usually permanent with MT, and (3) these comments then get indexed by search engines.
It is this last thing that is key. These blog spammers don't seriously think that they are going to sell much based on human beings viewing their spam. They just want search engine position because Google sees a link from such-in-such blog to the spammers web site as a "vote" by such-in-such blog for that spammers site, thus raising the spammer's site's rankings on Google.
Mischievous... but a very powerful marketing technique!
For examples, see the following:
http://www.google.com/search?hl=en&ie=UTF-8&q=%22diet+pills%22+%22mo... ype%22
Rob McEwen