Interesting article at: http://www.useit.com/alertbox/20041206.html
I found this part interesting (I'm 'cleaning' a friends PC this weekend because of a spy-ware problem)...Jakob Nielsen's Alertbox, December 6, 2004:
The Most Hated Advertising Techniques
Summary:
Studies of how people react to online advertisements have identified several design techniques that impact the user experience very negatively.
Advertising is an integral part of the Web user experience: people repeatedly encounter ads as they surf the Web, whether they're visiting the biggest portals, established newspapers, or tiny personal sites. Most online advertising studies have focused on how successful ads are at driving traffic to the advertiser, using simple metrics such as clickthrough rates.
Unfortunately, most studies sorely neglect the user experience of online ads. As a result, sites that accept ads know little about how the ads affect their users and the degree to which problematic advertising tricks can undermine a site's credibility. Likewise, advertisers don't know if their reputations are degraded among the vast majority of users who don't click their ads, but might well be annoyed by them.
Now, however, we have data to start addressing these questions. At my recent User Experience 2004 conference, John Boyd from Yahoo! and Christian Rohrer from eBay presented a large body of research on how users perceive online advertising. Here, I offer a few highlights from their presentation (my comments on their findings are solely my responsibility).
What's Bad
When users were asked how various aspects of online ads affected their Web experience, they rated the following attributes most negatively.
Another user entered the following comment on a major website's feedback form: "You people should be ashamed of yourself! I did not ask to have 3 pop ups come across my screen when I visit you. I do not visit singles sites, and I don't want to add 4 inches to my *****. As a matter of fact, I don't use any of the services that pop up on my screen. I think it is disgusting that you money hungry ******* have infringed on my computer for your own selfish gain. From this moment on, I am boycotting you, and I am advising EVERYONE I know to do the same thing. Down with you and your pop up ads."
Although it vividly illustrates user frustration with pop-ups, this second comment is unfair because the site didn't host or advocate the offending ads. The ads were delivered by "spyware" that the user had unwittingly installed. In addition to showing the strong feelings engendered by intrusive or irrelevant ads, the comment also illustrates the extent to which pop-ups have become associated with unsavory content.