Google is testing various headlines for the Local Service Ads. Two of them show the "Ads" label and one does not, while they all test different headlines for the ad listings.
This was spotted by Len who posted this screenshot on Twitter:
"See plumbers" versus "Here are plumbers" versus "50+ plumbers nearby" - I bet you the one without the Ads label does the best in terms of click through rate?
Forum discussion at Twitter.