Tough question, huh? I think 'banner retargeting' is great. You drop a pixel on your visitors and if they don't convert they start getting 'stalked' by your banners while visiting other websites. It's pretty much a genius idea and it's amazing what some people are developing in this arena.
But today I saw a chart related to the Generations Report 2010 created by the Pew Internet & American Life Project. This chart made me realize that right now no matter how cool and effective as pixel retargeting or behavioral retargeting is...good ol' email follow up is another form of highly effective retargeting...
Check this chart out:
So, according to the Pew study, E-mail is the most popular online activity among each age group. Also, we see that 94% of all US adults (18+) who use the Internet also use e-mail. I would say those numbers build a pretty strong case that you need to be capturing your site visitors' e-mail addresses and following up with them often.
Looking again at the chart above, we can see that 87% of all US adults who use the Internet also use search engines. Interesting? Yes, I think so. This means that combining your PPC and/or SEO with E-mail Marketing is a profitable combo.
Also, another great combo is using companies like AdRoll.com and FetchBack.com to retarget your site visitors with display campaigns.
Anyone else using retargeting of any kind?