Maybe I’m being a bit provocative here, but I don’t see SEO as a viable industry long-term.
Would you hire a company to produce a shoddy TV commercial for you just to turn around and hire a TV commercial optimization company to fix it?
If not, why would you be amenable to such a scenario with your web site? It just doesn’t make sense.
Search engine friendliness, as well as usability, should both be core competencies of the web developers. Don’t hire a web vendor that isn’t going to do a proper job of the website development from the get-go — including making the site “sing” for the search engines.
SEO isn’t a black art like Seth Godin opines . It’s scientific, measurable, and testable. And there’s a wealth of information online about SEO, freely available. There’s no excuse for a web design firm to deliver anything but a website that’s been optimized for search engines.