Those are minor compared to some of the crap I have seen.
1. “No follow” or “No Index” added to links or page so you dont get credit for the exchange.
2. You go and check a few weeks or months later and the whole page is gone or the links have been removed. You email the person and they apologize and blame a site update. They resore your link and when you go back two months later its gone AGAIN.
3. They remove links on their site to the actual page your link is on. If you bookmarked where your link is or use link verification software it still sees the link and page at that url, but Search Spiders never see it because it’s not linked to within the main site!
Etc… Etc…
If people put the same effort into bulding a quality site that they do into conning one way links out of other webmasters they would be rich.