How can you tell when a viral marketing program is working well? When Zynga spreads it to several of their top games. Last week we noted that the horse stable promotion helped drive FarmVille over 30 million Daily Active Users soon after it was launched because it promoted its heavy and hard core users to proactively request gifts from friends to complete the building.

Now the same concept has spread to Cafe World and Mafia Wars. In Cafe World, users must collect shelves, jars and lids to create a spice rack:

In Mafia Wars, as part of the revamping of the way properties work in the core New York chapter, users have to collect blocks, car lifts and other material to create the chop shop:

So are they providing the same daily active user punch that the horse stable did for FarmVille? So far they aren’t, but to be fair these just launched late last week and the Facebook-reported DAU numbers have been sporadic of late.