One way to dethrone the king of local online advertising is to simply acquire it.

Despite its very familiar brand, Yelp's (YELP) market valuation is "only" $6.1 billion, potentially making it attractive for a a big Internet or travel company to buy.

Last week, Goldman Sachs (GS) predicted mergers and acqusitions (M&A) in the Internet world will accelerate since companies have so much cash on hand and they see potential benefits of scale.

There's already been over $50 billion of M&A action in the U.S. Internet sector this year, including Zillow's (Z) $3.5 billion acquisition of Trulia (TRLA).

One potential target is Yelp, which Goldman awarded an M&A score of 2, or "medium." That signals a 15% to 30% probability of a buyout. The bank also hiked its price target to $78 from $74 based on the increased likelihood of a deal.

"We believe Yelp's robust local content, relationships with agencies and SMBs (small businesses), and wide consumer reach could be valuable for online advertising and travel companies," Goldman wrote a recent note.

Internet giants like Yahoo (YHOO) and Priceline (PCLN) would seemingly have the cash and borrowing ability to pull off such a deal.