I understand completely what you are saying. I own a design firm in Atlanta, Georgia and we do a similar tactic. I personally, think it is important to vary your keywords you are targeting. It may look fishy that all your back links are keywords for web design.
A back-link from a site serves more of a purpose then just keywords. If the site receives a lot of traffic and people love the design they may click the link to see who designed it. We use the following anchor text " Powered By, Atlanta Small Business Web Design, Small Business Web Design, Developed By, Designed By and our link www.treelifedesigns.com
