This question already has an answer here:
Does anyone else want a way to flag an interesting question?
I'm thinking of a case where a new question comes up on the front page of a site, I can't answer it, BUT I would be interested in the answer.
Especially on the more general interest sites than Stack Overflow where you are browsing general questions rather than looking for specific answer to an immediate problem. Since it is likely to disappear from the page before being answered, all I can do is bookmark it in my browser or post a pointless comment "to follow".
Propose a way to flag an interesting question and have new activity on this question show up on my account page in the same way as an activity on a question/answer I have written.