Well look at it this way.. Personally i only use google search engine to find the information i need. I know yahoo is used alot in the USA etc. So all the other little ones wont get that many searches therfore no traffic
I am starting out in the affiliate marketing and i only use Yahoo Search Martketing as i find it alot easier and cheaper then google adwords. Especially as i got $100 free in credit so thats a bonus
Now i have a credit card i may try using MSN's version of it to see how that goes (only if i can get a free coupon for credit to start out)