"Of course it is partly marketing in order to get you to purchase a world membership. (I'm not knocking world membership, I have it and need it.)
But you have to develop a certain immunity to shaky green leafs. I have 10,000 that I haven't looked at yet because I have [finally] learned to research systematically."
I suspect it's more marketing than anything else since Ancestry had to set those hints up to be handled differently than others. I've had the World membership in the past but I have enough to do on this side of the pond and money is tight in this economy so I don't have it now.
As for researching systematically, everyone has their own system. This is a long term hobby for me so my system can be a little loose. lol
A lot of times at night when I don't feel like doing anything else I'll scan my tree and review the hints for a few folks. Trees are ignored by default and the bulk of the hints I see aren't news but occasionally I stumble across a gem.