Currently, the C# tag has 14,914 unanswered questions. I though I would help and started at the last page (maybe some didn't have an answer yet or I could come up with a better answer) but this is no use. Many questions are out of date and many users haven't been active for a long long time.
Is there a way to get this number down?
A few ideas:
Limit ability to ask questions if your acceptance rate is below 80% (wild guess at the number);
E-mail people;
When someone logs on a again, show that nice orange bar saying that he/she has unanswered questions older than 30 days (again, wild guess);
Do something with old questions that did not receive an answer;
Probably many many more suggestions.