As long as you can get over any qualms about giving Google more control over your personal information than they already have, filling out a profile could be a good way to promote a legal practice and make sure that you actively participate in your online identity, rather than leaving it entirely to chance.
But Google Profiles isn't the only way you can tend to your online presence. Microformats, particularly the rel="me" tag, can help you to connect all the various sites that you control or that are about you to a "social hub" online. Search engines and other applications will then take notice of this and give you some serious link juice that could raise a page of your choosing to the top of search results for your name.
Just be sure to also add links on your blog to your Facebook and Twitter profiles that also have the rel="me" tag, or search engines will ignore the relationship.
Using rel="me" can be a great way to control your online identity and the marketing for your practice. Instead of searching through random and possibly confusing (or worse) search results, users will get your blog or web page as a top result and can go straight to that page to learn more.
It's not a magic bullet that will automatically fix all your search engine optimization concerns, but it can be a powerful tool.
Google Profiles and Creating a 'Social Hub' on the Open Web (monkey_bites)