How big of a market is SEO? What are some of the biggest SEO companies and why is it such a long-tail market without industry leaders?

Here's a list of TOP SEO firms: http://www.topseos.com/rankings-of-best-seo-companies Re: firms on that list,  I can personally vouch for Ymarketing, a HubSpot Certified Partner, as being very good. I'm not sure exactly why there's no clear leader in the space. But, it's not that much different than the fragmentation of the marketing services industry, in general.   There's 1,000s of small PR firms, web design firms, marketing consultants, social media consultants, etc. Secondly, SEO should be done in the context of a broader internet marketing strategy. For example, web designers and developers should be experts at SEO, as it's important to choose keywords before creating pages, navigation, etc. PR firms should be experts because content and press releases for link building are they key to improving search rankings. Further, anyone that's doing SEO should be measuring its impact on traffic, leads and sales, whether sales occur online or off, which tends to be something that all types of marketing firms must obsess over. SEOMoz does not offer SEO "services" btw. Like HubSpot (my company), they provide software. Their software is used by many top SEO firms, but there's lots of SEO software providers out there. Once again, I'd recommend finding software that helps do SEO in the broader context of internet marketing. Specifically, SEO software should be integrated with your blogging software, cms software and web analytics software. If your providing services to SMBs, it's hard to do SEO efficiently unless the SEO data can be used to quickly inform decisions about content, optimization, content promotion, and how all of that is converting into leads and sales.

SEOMoz's blog is great for learning SEO and staying abreast. It's wise to get a handle on SEO fundamentals, techniques and terminology before you hire an SEO company. I'd even go as far as hiring an SEO consultant for personalized SEO training. Your ability to champion and foster SEO best practice throughout your organization is key to your success both short and long term. Here are just a few of the SEO tools that we use here at: http://www.searchoneweb.com to look at On Page issues: http://www.woorank.com http://gtmetrix.com/ http://wave.webaim.org/ http://www.webuildpages.com/seo-tools/spider-test/ Like I said before, I would hire an SEO consultant for a "fast track" training session/s before hiring a company. It's relatively inexpensive and will save you hundreds of hours of wasted time, if time is an issue for you. There are so many industry leaders it really depends on your budget. Do you have VC? Are you Bootstrapping? What is your business model? When are you projected to make money? How will you monetize? Competitive landscape and the amount of funds it will require to dominate your market. I could go on but you get the picture. Hope that helps a little and all the best for you!

SEO is a very big subjects, in my opinion a company which is looking mix marketing solutions had to have the following: - content writers - in site/site map seo/seveloper experts - seo expert with strategic and marketing approch - total web awareness. these all services are very expensive, but if you will use marketplace of professional who deliver for reasonable prices, you'll find the new value of $10 -- this you'll probably find in http://jobsfor10.com.

I actually think there are a bunch of industry leaders. Just to name a few, you have: Bruce Clay, Rand Fishkin, Aaron Wall, Vanessa Fox, Danny Sullivan and the list goes on.

In my opinion every website should have some level of SEO. Therefore, the market for SEO would be as large as the amount of websites. I haven't seen any exact number of businesses with websites and the percentage that currenly utilize SEO. http://eMarketer.com may have some reports on this in the US. I work for an SEO company in Canada http://www.9thsphere.com

Think of SEO not as a service, but as a best practice. Implementing best practices to make sure the search engines can find the information you are providing. Think of those 100% Flash driven websites. Do we see much of those today ? No. We all know why.