A Google Places Help thread reports some business owners complaining that their business listings on Google Maps continually gets hijacked by competitors. One person said, "on almost a daily basis my client's listing gets hijacked."
Linda from the Google Maps team said in the thread:
Sorry for the trouble you're experiencing. Thanks for notifying us of this issue. We are looking into this.
For others that are experiencing similar issues, please post your business listings URL from Google Maps.
So if you have experienced this, join the Google Places Help.
Forum discussion at Google Places Help.