Of course they're intelligent. It's more likely that they're looking at more solid leads or waiting for forensic results. The internet may be the domain of the police technie guys rather than the detectives themselves.
Plus, I don't think the police would reveal in a statement that they have people whose sole job it is to monitor internet activity. You can bet they are though.
Well one of the contributors to this thread has made it as clear as possible without explicitly saying it that he is a police officer involved in the Joanna Yeates murder enquiry. And unless my sleuthing abilities are misleading me his choice of screen name very strongly suggests that he is a detective chief inspector (not Phil Jones) who has been widely named in the media as connected with the case. At least, if that is not the reality, someone must be setting out to give the impression that it is.
I've been wondering why his contributions haven't been treated with more respect.