On a recent discussion board in LinkedIn, a member of one of my groups asked the question about the credibility of Search Engine Optimization (SEO) experts. They went as far as to refer to them as "Snake-Oil Salesmen", which is a pretty funny analogy.
Here's a way to answer this question. If it has anything to do with technology that is rapidly changing, and someone refers to themselves as an expert, then they are more than likely not an expert. Just ask some of the big tech companies that are scratching their heads to figure out how Google is flat out "getting it done". Or look at the job postings that actually look for candidates with 12 years of experience with software that's only been on the market for 5 years. Speed has its downsides like any other performance enhancer.
My answer to the inquiry was to look at the "branding experts" during the web boom. Where are they? What did they accomplish? I won big on a slot machine ($400 on a quarter slot) in Vegas a few years ago. I had a strategy going in, and it worked. However, I'm hardly a slot machine expert. Rather, I'm part of a statistic that forms the inevitable bell-curve. Even if I won a few more times at different casinos, that still wouldn't make me an expert - spreading the gospel to little old ladies at the nickel slots.
Everything has to be taken within the context in which is succeeds or fails, and nothing really works when you make the assumption that all other things remain constant. Are there good SEO professionals and bad ones? Yes, but there are more variables to improving online sales and site traffic than pay-per-click strategies. Can a good SEO professional help you realize an increase in site traffic or revenue? Yes, but the increase really depends more on the product you are selling or the content.
The reality in business is that "Snake-Oil Salesmen" are in business because there is a demand for snake-oil. Yesterday it was branding, today it is search engine optimization. The free markets will remain true. The more you mess with them, or try to cheat them, the more they will seem like huge obstacles to realizing success with your business. Stick to the fundamentals.