Google openly publishes guidelines on landing page quality score issues. Quality score is that factor, when combined with CPC, which helps determine how much prominence the search engine will give the paid search ad.
In these guidelines Google says three types of sites will always be penalised. In fact, should Google receive complaints about such sites, their ads will be banned.
The unlucky three categories?
Data collection sites – those who offer freebies, competition entries, etc, in return for the collection of private information.
Arbitrage sites – those which simply show ads back to the visitor
Malware sites – those who knowingly or unknowingly install software on the visitor's computer