The "Welcome back, If you found this question useful, don't forget to vote both the question and the answers up" banner has had its share of complaints. (ref, ref, ref) While it clearly has value, its negative impact could be reduced by automatically hiding it when the user does what it asks them to. That is -- make it go away when the user votes.
Advantages I can think of:
- Since the user is voting, they clearly already understand point of the message.
- The click targets for voting are bigger and thus easier to click than the very narrow "close this message" link on the banner.
- The vote buttons are already familiar to any regular user.
Disadvantages that I can think of: