I hope I don't get flamed for this but well, as they say, there is No white or black, just shades of Grey (or Blue?)
You can use Yahoo Answers service to get decent traffic. Not to mention, a properly phrases question can easily get you on top of Serps.
The rest is on you. But don't spoil a nice service by spamming it since it wont help you much.
but if u try to add to much
but if u try to add to much of url's in u r answers yahoo simply block u
ya, that's why its important
ya, that's why its important to make it look real. Infact, it will help you alot if you indeed try to give a genuine reply.