Jest - It's not necessarily the volume of traffic but the quality of the traffic.  Most of these auto-completed (or "suggested") searches contain long tail terms which indicate the user is much more likely to convert to a customer.   My $ .02

Eliathah - I agree.  Blog commenting is extremely inefficient use of time. I wonder how many of the people who promote blog commenting as a method to obtain traffic would pay someone else to put "meaningful comments" on relevant (no-follow) blogs.  I wouldn't and I doubt many people would.