There is a new scam brewing around Google Maps reviews. Mike covered it well at his blog, but I was also planning on writing it this morning, so why not.
A WebmasterWorld thread and Google Places Help thread (didn't know about the Google thread, thanks Mike!) all discuss this scam.
In short, there are people leaving negative reviews on your map listings. Then shortly after, they are emailing you and offering to remove the negative reviews for a fee. On the other hand, there are people offering this as a service, add negative reviews to your competitors for a fee.
A senior WebmasterWorld member, said:
This has happened to two companies that I work for in the past 6 months. Wondering if anyone else has seen the same...A bunch of negative reviews are posted in Google Maps for a particular company. About a month after the posts, the company gets a call and is told that the negative reviews can be removed for a fee... typically $400. We have been flaging the reviews, tey it seems to take google forever to even take a look.
Forum discussion at WebmasterWorld and Google Places Help.