So who is winning in the mobile ad business?

Never mind the fact that nearly 40 percent of mobile ad clicks are either accidental or fraudulent — the folks from eMarketer say that mobile ad revenues in the U.S. will grow from $1.45 billion in 2011 to $6.62 billion in 2014. The New York-based research group projects that by 2016, the U.S. mobile advertising market will be close to $12 billion.

It should not come as a surprise that search-and-advertising giant Google (s GOOG), which also owns Android OS, will continue to dominate the industry and will grow at a monster speed. However, Pandora and Twitter stand out for their mobile ad revenues.

According to a eMarketer press release, “On a net basis, Pandora Media (s P) has emerged as one of the strongest U.S. mobile display-ad sellers, and its share of the total U.S. mobile display market is expected to reach 20.5% in 2012.” By 2014, Pandora will have 7.5 percent of the mobile ad market, while Twitter will come in at 6.7 percent. Note: One way that Pandora has reached these heights so quickly is by putting its mobile ads in heavy rotation. For me, that  has killed some of the joy of using the app, and it may ultimately turn off other users of the service as well.

While Twitter is beating Facebook as of now, it won’t be long before Facebook makes a comeback and takes about 9.5 percent of the market in 2014. Apple’s (a AAPL) iAd continues to struggle and perhaps it is time for Apple to rethink its ad foray and instead go back to its knitting.

As a heavy mobile web user, I would be grateful if these giants could just come up with better and smarter mobile advertising formats, to replace the banner-based advertising that is not optimized for the small screens.