It seems like this topic has been a bit of a bandwagon as of late, and I’ll give it a shot, jump on, and throw my $0.02 in.
This has always been something that’s proven difficult in the more than four years that I’ve been in this industry. In my history hiring and training SEMers, I’ve personally interviewed and hired over 30 search engine marketing specialists, and trained well over 100 people (between sales, service, and search marketing specialists). With whatever credibility that lends, I can honestly say that finding and hiring experienced search marketing specialists is the most difficult.
The reasons are obvious: This is a new industry, those with knowledge and experience are mostly self-taught (and often independent consultants), it is not a glamourous industry (if it were, there would be a greater interest), and the combination of marketing and technical aptitude to truly become an expert is quite unique.