The service is not maintained by the GSA, but is introduced by customers of the product. The included web 2.0 sites do change their layout and how they work so often that they cannot be kept active by the GSA team alone. However, the service keeps adding new engines and fixing each of them as they change. Although you will need to pay for this service, tracking changes can be a very time-consuming task.
SEREngines.com has more web2.0 engines
SER Daily Verified Lists – 1LinkList
Asian Virtual Solutions
GSA SER list
Automatic approval list
SERLinks / SERLinks
SER Verification List
SERocket.net
Link plug-ins
GSA SER Verification List