A court ruling that Vonage cannot acquire new customers could have a sizable impact on the online ad market, writes ClickZ. The U.S. District Court in Virginia ruled that Vonage has infringed on Verizon's VoIP patents and barred it from acquiring new customers - though a temporary stay of that ruling has been granted.

Vonage was the top online ad spender in 2006, coughing up more than the likes of Walt Disney and At&T. Last year, its monthly ad spend varied from $6.7 million in November all the way up $31 million in January. In 2005 the company spent $331 million on all media spending.

Vonage is running a good amount of its ads through networks, including AOL's Advertising.com and ValueClick.

Vonage's potential disappearance from the ad market means the loss of contracted income - and publishers running Vonage ads will have to resell that inventory.

Publishers, though, are apparently not too worried about reselling that inventory, saying plenty of potential advertisers are out there.