http://scobleizer.com/2007/06/20/a-look-into-an-search-engine-marketers-life/

VIDEO interview by Scoble with Search Marketer... this
SEO agency has clients that actually have ONE MILLION KEYWORDS

and they manually do the SEM, according to the interview....

comparisons of Google Yahoo and MSN search marketing platforms

They pick Google as being the one really worthwhile