Ancestry World Tree mirrors content available at Source:RootsWeb's WorldConnect Project. It is a collection of user-submitted trees. Sourcing is supported but use is optional, and the quality of information obviously varies by user.
Citation should be limited to where no other source is available, due to the uneven quality of the trees and the ability of users to delete the information at any time. Citations should include specific URLs or at least the name of the tree and submitter.