Science hat on: Eh, looks to me like someone taking one study that agrees with their viewpoint and running with it. Until that study is confirmed by findings in other studies it means little right now (actually preferably a meta study). Whenever someone quotes just one study in something like psychology and its not a meta study, be very suspicious.
Speculation: For some people, definitely keeping things private is a good idea. No question. Whether this can be generalised to everybody or whether we can even talk about goal setting for people in general is a very complicated question.
We can break the issue down into two sections:
a) Should we set goals? If so, what kind of goals?
b) Should those goals be public or private?
a) I say yes and I'll borrow from the therapy I've gotten and say they should be SMART goals:
http://en.wikipedia.org/wiki/SMART_criteria (comes from management theory originally but has found its way into psychology it seems)
b) I think it comes down to your personality and mood. If you enjoy discussing your goals and you progress towards them then it makes sense to be public about them. If the fear of not achieving them makes you very embarassed then not going public makes a lot of sense (but I'd argue that going public might not be a bad idea so you can see that failing a goal isn't the end of the world). I think going public also keeps you grounded in reality too to a fair extent as if you start setting obscenely ambitious goals people will call you on it. This is important as setting practically impossible to achieve goals is not a good idea for all but the most resilient and driven people.
TL;DR: Set goals, make them public, learn that failing is ok and not the end of the world, dust yourself off and set more realisitc goals and you'll have learned something valuable about how to deal with life. It's all too easy to start beating yourself up if you keep your goals and your self-recrimination private. Just as people will call you on it if you're overly ambitious, they'll call you on it if you're being overly negative too. At least if you're in a nice community anyway.
