Overlinking is the practice of linking to too many things, especially on wikis.
Overlinking can be helpful, because it encourages people to expand the information contained on the wiki.
On the other hand, overlinking that is carried to a ridiculous extreme can be quite annoying.
Naturally, some people oppose overlinking because it supposedly hurts the eye. That is quite a lame reason.
You meant to say "lame excuse", right? Some like to link because they think the text looks cool when it is blue and has a line underneath it.
See also The Answer.