When you're selling an advertising medium, virtually all advertisers will ask how can they "measure ROI". What really seems to me is that most of this is just talk. (
http://kariobrien.files.wordpress.com/2013/07/marketing_roi_...)
I'd argue that fraud is a big problem because it affects ROI.
Especially, it affects 40% of mobile ads, which means that you just wasted 40% of your campaign's budget.
It's estimated to be between 2% and 19% on online ads, with those 2% being acknowledged by Google, who is probably one of the few providers that actually does something to prevent it.
I think this is a challenging topic. There's an economical problem in plain view. Why are advertisers ignoring it? Lack of alternatives?