I'll tell ya what, I'll pull myself out of this discussion and instead quote some of the excellent market analysis that's included in Marketing Sherpa's brand new Search Marketing Benchmark Guide. Here's what they suggest, based on their extensive research:

The big marketing debate over SEO has never been whether or not to do it. It's self-evident that you'd want your site to appear near the top of free rankings for keywords important to your brand. Instead, the debate has always been whether to outsource or handle SEO in-house.

According to this year's revenues, the keep-SEO-in-house school of thought is winning. This is amply borne out when we examine the actual percent of total search marketers who run SEO in-house. Last year that percent was about 74% and this year it's ... 74%.

Any growth in the SEO outsourcing industry has mainly come from current accounts getting larger and from general overall growth in search marketing as a whole.

(Worth noting: we found nearly the same to be true for the paid search advertising (PPC) agencies as well. There, 73% of potential clients choose to keep campaigns in-house.)

If you're a client-side marketer, this data points to a significant ongoing competitive opportunity for your online presence. According to our 2005 data, marketers who outsourced SEO saw a 110% lift in overall site traffic within six months, whereas marketers who handled SEO in-house saw a 73% lift.

In short, if you hire an expert for SEO, you tend to get significantly better results. (Note: we do not offer SEO services, nor accept advertising from SEO firms. As a research firm, we have no reason - beyond the data - to be making this recommendation.)

Here's an interesting graph about keyword buying trends to consider:

Why is keyword growth slowing for B-to-C? Two factors are at least in part responsible - the first being that cost per click continues to rise for many markets.

The days of easy find five-cent clicks are for the most part behind us. In addition, the trend in 2005 was to expand search success by doing a "landgrab," reaching out to every conceivable keyword to see what would stick.

However, these massive campaigns are not as competitive anymore - anyone with the budget can do them with easy-to-use keyword expansion tools provided free of charge by search engine.

Plus, we have plenty of anecdotal evidence revealing that experienced search marketers are refocusing on doing the best job possible with the most important keywords for their brands. They feel it's better to do an extremely good job of copywriting, bid management and landing page conversion optimization with fewer search terms than a slightly more slapdash job with more terms.