Lately, Lee Odden has written a post, discussing whether web designers without any SEO knowledge are evil, or should exist as cash cows for SEO consultants.
Apparently, every SEO (and web designer) has his own answer to this question.
Should SEOs educate web designers?
Of course, we can neglect web designers and milk them (and their clients) for ages. But how will that go along with our desire to be working on something more complex and challenging? Do we want to perfect our knowledge and skills? Do we want to make a positive impact on the Web?
Moreover, knowing web designers, there will be much more things after you educate them. Crawlability (search engine friendliness) and on-page optimization is good, but how about conversions, accessibility? You'll spend plenty of time training your web designer to think about "don't make me think" and "conversions", let alone AAA accessibility compliance.
I guess this is a common way of improving things. Remember the websites of the early 90s? What do you see now, something a bit better?
Why learn SEO?
From a designers perspective, at least knowing how search engines work will allow them to create SE-friendly websites. This will drive more traffic to their clients' websites and make their clients happier, so the designers will get more referrals and more loyal customers.
After web designers make good websites..
After web designers create more or less SE and human friendly websites, SEOs can still have their jobs, because no websites is perfect and there always will be something to fix. Moreover, just having a crawlable website doesn't get traffic alone. The website needs some promoting and that's what SEOs can do (now transforming to marketers or jacks-of-all-trades, really).
Overall, in my opinion, SEOs should rather educate everyone involved, not just web designers, because it will improve the overall Web experience for everyone, not just the web industry people. And there always will be something to work on, such as usability, conversions, accessibility, customer loyality and so on.