Getting top 10 search engine rankings is the goal of most search engine optimization projects. It makes sense that if your in the top 10 for a keyword related to your firms practice, that you will get some traffic from people looking for the type of law you practice. How about if you were able to get ALL TOP 10 rankings for certain keywords!!!
Ive got one client who has a number of different sites including many mini sites that are focused on specific practice areas such as corporate law, tax law, litigation, estate planning and others and most all of them are listed pretty well in the organic search listings.
At MSN for the keyphrase Chicago Tax Law the firm has the first 7 spots and then also the 10th place for a dominating 8 out of 10 top 10 rankings! Its harder to achieve that at Google BUT they do have 3 out of the top 10. 5 out 10 at Yahoo.
Having multiple sites can be a very good idea and a way to focus on different sets of keywords. Yet its important though to not just repeat the same content on multiple sites, you must have unique content in order to have success. The more unique content, the better, content is and always will be King!