Investment firms have to be careful with how they present themselves to the public. There’s a fine line between touting your skill and making unrealistic promises, and anyone who goes too far is likely to get a visit from the Securities and Exchange Commission. One rule meant to clarify what’s acceptable is the ban on testimonials, because they could give the impression that one client’s positive experience will be true for everyone, but in the age of retweets, likes, and open Facebook Inc (NASDAQ:FB) groups the line had gotten a little blurred. The SEC has now released guidance on how…