Between February 2006 and January 2007 the National Benefit Fraud hotline received 211,355 calls according to a written answer from the DWP. Some of these calls may have been the same person checking up on the status of their snitching, but even so it's quite impressive.
Of course, the National Benefit Fraud hotline is an 0800 freephone service, and knowing what sort of deal the Government blagged from BT or other third party Telco is an unknown quantity. generally speaking though a company wishing to have an 0800 number gets charged around 4p per minute for the calls coming into it.
If we assume that each call probably last at least 2 minutes (holding and then speaking to someone), that makes a rough cost of around £170,000 for calls, which frankly isn't that bad.
However, there is a downside (isn't there always), during the same period there was a massive 608 prosecutions for benefit fraud as a result of evidence provided to the hotline.
That represents about a 0.28% success rate of calls which lead to prosecution. This could suggest that the line is a bit of a waste of money, or it could represent the fact that there are a lot of people out there who really hate their neighbours, or maybe both.