05.03.07
Stay away from 2nd tier engines?
Gordon Choi wrote an interesting post about why not to advertise on 2nd tier pay per click engines. He explains a few strong reasons to stay away from them. To reinforce his point take a look at this chart. 
With a majority of users searching on Google, Yahoo, MSN, ASK and AOL the time you spend setting up and troubleshooting those smaller engines may have been better spent optimizing your engines that drive more qualified traffic. Also, most 2nd tier pay per click engines get their sponsored results from one of the bigger engines, so your ad will most likely already appear there.
