[magikbum]

It could simply imply it's "illegal" due to the contract those publisher sign with the SSPs and Exchanges that clear their inventory. i.e. "; iv) create "forced visit" traffic; v) create invisible or nested IFrames loading pages or ads; vi) intentionally falsify clicks: vii) modify or obscure display of ads; viii) fraudulently generate requests or clicks; or ix) use any means of artificially generating ad impressions or clicks, including third-party services such as paid-to-click, paid-to-surf, auto-surf, and click-exchange programs."