Unblock and get infected
The last time I disabled my adblock for a site that I very explicitly wanted to support, it took about 5 minutes before my antivirus flagged up than an ad was trying to breach containment and access information that it shouldn't have.
That's the big issue for me. I don't mind (too much) having uninteresting ads. The problem is that ad networks are STILL bad at preventing malicious ads.
Oh, and ones that break out of their spot on the page and cover up content.
Ads should be adding value. If your ad is preventing me from doing what I want to do, then I'm not going to want to purchase your product. You've just annoyed me. If anything, you're now blacklisted. If I happen to notice your ad while I'm doing stuff and it peaks my interest (without interfering with my activity) THEN I might further investigate your product.