netmeg - 2:25 pm on Aug 2, 2012 (gmt 0)
As goodroi says, it can be done, but it's kind of tricky. I have a client who has three websites in the same industry and there is some overlap on search terms. On one he sells consumer products. On another, he sells training and certifies people for servicing, and a third is an industry blog. Things shift around a lot in the SERPs, but the content and focus of the sites is different enough between them that they all do pretty well.