They could come from people simply browsing, not in itself fraudulent, but still bound to dilute ROI statistics.

Either way, as long as click fraud can be priced into the ROI (return on investment ) equation does it really matter whether the money is going to the search engine or the fraudster? Besides, arguably it is the search engine problem, as a lower ROI is likely to result in small ad spends coming their way for them to take their slice from.

What do you think?