Well, I don't know about marketing, but we're using it to build two sites, with a third in the wings.
www.greatestnetworker.com
www.ercmembers.net
www.swainmortgage.com
In the case of my favorite, a private site called www.ercmembers.net, we are incorporating as many modules as we can, to make the system wide open for the use of our members. While there are users starting to use it, it isn't "Grandly Opened" yet! We have a group of people (approximately 500) who will initially be subscribed, and we're looking for about 1000-5000 members, we think.
So far, we have implemented User Homepages, WimpyPoint, File Storage, Classified Ads (with Auctions), and Whois-online/Chat.
To date, we haven't decided what to do with/about forums, but they will be very important for collaboration among our users, as is Wimpy.
We will be incorporating E-commerce with a paypal link setup, as well as Credit Card Verification.
