I suggest that you do not part with any money until you have visited the property and you have a proper signed contract in your hands. This won't guarantee against fraud, but it will avoid some of the scammers.
If this happens to you please tell the police, and let me have the details of the advertisements so that I can delete them.
Another scam currently doing the rounds is to email you asking you to call back on a premium rate (eg 070) number - you get to pay to listen to a recorded message containing lots of waffle, and there's no real room or tenant on offer of course.
All this data is Copyright © 2006 Tim Ward and/or Copyright © 2006 Brett Ward Limited. You may not sell this data. You may use this data in other ways provided that you include this copyright notice and a reference (a link will do fine) to the Cambridge Accommodation Notice Board.
Some care must be taken in interpreting this information. Advertised rents don't necessarily tell you how much rent was eventually paid; some of the advertised rents do include various bills that others don't; some advertisements are for several rooms in which case the recorded rent is only for the cheapest.