I agree that SEO is a job often best left to the pros, but I strongly disagree with the blanket statement that it must be done only be the pros in order to be successful.

As with any business model, it depends on who your target market is. If you are the first in your industry to consider SEO, as a small business owner you will do just fine with the helpful resources that are scattered across the web and can, with a little work, rank quite well organically.

If you have a unique angle to your product in a saturated market and you can build content around specific keywords that your niche uses - then you can do SEO yourself.

As with everything, its all relative to the amount of competition you have and how much time they are spending perfecting their SEO strategy.

If you are in the car, travel or alcohol industry - good luck, hire a great SEO team.