What the hell is wrong with some webmasters who want link/banner exchanges?

I find that some sites with whom you exchange banners/links with, that all of a sudden your link back just vanishes one day...
So, I write them and ask what happened, and hear nothing back.

Then I re-submit my url and they reject it????
After I have had them on my site for months...
Nothing has changed...I read their rules and follow them to the T

So, what the hell...this seems to happen way, way too many times with my gay sites.

I never have a problem with my straight sites

Is it just me or does this happen to anyone else too?