I was going to retag a question but it didn't have the link. Also the edit link was grayed out. It is 31 minutes old and I have they are there on other questions. What situations does this happen in?
Hover over it. The link will tell you.
It's in the hovertext.
:) As mentioned in the comments, it can happen for many reasons, most likely the edit queue is full. The link used to be removed completely, but a recent feature change leaves it on the page, greyed out.