Once a visitor hits your site, how long do you have to convert them?
In web marketing and usability, the long-held standard has been the 7-second rule, but more recent studies would tend to indicate you've got a bit more time than that. For example, problogger noted back in March that 37 seconds was about average for a blog visitor - they surf a bit more in general and many of the visitors are devoted readers (as this ClickZ report would indicate). I would venture a guess that despite stats showing longer stays, the "first impression" magic is still created in those critical first few seconds.
I'd also argue that as generations become more savvy to the web, chances are that number will drop. Savvy web users that have grown up using blogs, forums and the Internet in general will be able to discern information in 4-5 seconds, meaning the window is getting smaller.
Does this spell trouble for the e-commerce, ad-serving or content-sensitive sites on the web (i.e. all of us). Again, I'd go against the grain - my feeling is that this increased knowledge and experience on the web will acutally bode well for content & site creators. A tech-savvy population will be spending more time, more dollars, and more effort online, whether it's buying goods and services, researching or interacting socially.
What will be critical (and is already of great worth) is those initial few seconds. If the design of a site is offputting, your abandonment rates will skyrocket. If it's hard to find the keywords they searched for prominently on the page, they'll leave. If a site isn't intuitive or fails in any part of its functionality, your visitors will come to a screaching halt. The reality of a web-savvy generation will be increased expectations in every area (design, usability, functionality, personality), from every site.
The new Internet bubble is going to make many of us rich (and many more very comfortable), but your sites are going to have to cater to a new, pickier generation of visitors and do it in just a few seconds.
I think it's also worth thinking about load time. A visitor won't wait long for that front page to load, even if it's gonna be eyecatching and create a great first impression.
I think there is going to be a lot of market segmentation. Walking past the magazines for sale at a newstand you see a hundred or more covers, each designed to appeal to a target demographic. I suspect home pages will follow that pattern.