It seems like an OK idea, with two flaws:

1. Sending people email is annoying.
   Part of what I like about Stack Exchange is the only email I get is the stuff I sign up for - when sites start sending me "reminder" messages I get cranky and tell procmail to do unseemly things to their messages.

2. The Stack Exchange inbox is a great place for this, unless the user never comes back to the network.
   The kinds of users who don't accept answers will probably be hit-and-run users ("I got my problem solved, why come back and bother with that whole participation thing?!"), so the notification icon won't ever bother them if they don't see it.

   The converse to this is that people who have a question migrated somewhere and forget about it but are active on other sites will see the notification, so this one may be a wash...

It seems like an OK idea, with two flaws:

1. Sending people email is annoying.
   Part of what I like about Stack Exchange is the only email I get is the stuff I sign up for - when sites start sending me "reminder" messages I get cranky and tell procmail to do unseemly things to their messages.

2. The Stack Exchange inbox is a great place for this, unless the user never comes back to the network.
   The kinds of users who don't accept answers will probably be hit-and-run users ("I got my problem solved, why come back and bother with that whole participation thing?!"), so the notification icon won't ever bother them if they don't see it.

   The converse to this is that people who have a question migrated somewhere and forget about it but are active on other sites will see the notification, so this one may be a wash...

All that said I have no problem with (2) above - it can't hurt (much), and it might help...