When last month Google began providing data on "invalid clicks," some advertisers had their fears of click fraud confirmed - nevertheless they remain unfazed, writes MarketWatch, based on an informal survey it conducted of Google advertisers.

Like spam and viruses, click fraud may be irritating, but it's part of the current ecosystem of online marketing, advertisers seem to be thinking. The story quotes Frank Watson of Forex Capital Markets asking rhetorically: "A certain amount of mail goes missing - are you not going to write letters? Airlines occasionally crash, are you going to stop flying?"

"Click fraud is like any other business risk; you should take appropriate steps to reduce the risk and gather firm data of any fraud," Duncan Perry, a click fraud expert and U.K.-based consultant is quoted as saying.

The scope of the controversial problem is itself an issue of controversy. Some say up to half of clicks are fraudulent, whereas several studies place the figure around 15 percent.