Portals play the affiliate game too. Up to half the space on a portal front page may be taken up by affiliates and adverts. Most visitors will ignore them after a couple of visits. From then on, they become a constant reminder that the aims of the portal and the aims of the visitor are not the same. It's all a matter of degree.
Most Web users are aware that advertising and affiliate programs pay the rent.
In most cases they accept a touch of commercialism with good grace. As they become increasingly familiar with the Web, they attempt to ignore banner ads, which then become subliminal and therefore work in a different way. It's when commercialism becomes intrusive that it spoils the party - when it becomes commercial overkill.