Do you make clients sign a contract for SEO services? Often signing on the dotted line gets overlooked. A scenario summarized by Search Engine Roundtable makes clear whey it's important.
Basically, SEO Gal got stiffed for payment. She optimized a site for a Web designer. The client's site ranked on the first page of Google for five of the keywords within a few weeks, but the client refused to pay because the site was not listed above his competitors'.