From the Mafia Wars Fan page:
In honor of reaching 10 million fans on Facebook, Mafia Wars will be giving away a few tokens of their appreciation starting March 30 (12:01 a.m. PST) to March 31 (11:59 PST).
For 48 hours, Mafia Wars Facebook fans will be able to the following:
* Double mastery in all cities (New York, Cuba, Moscow and Bangkok)
* All fights will produce 25% more experience
* Everyone who plays during this even will receive a limited edition item called the 'Heavy Hand'
Double mastery in all cities is unprecedented! There has never been anything like that before. This is the perfect time to make a new account and blow through the entire content field. Last time there was a double mastery bonus for New York, I was able to take a brand new account through New York (entirely) within just a few hours, following the principles outlined in Mafia Wars Compendium.
With double mastery in ALL cities, the only thing stopping you from mastering all content in game is your ability to come up with politico corruptos, pirates, and drug shipments. The thing with double mastery is that you have so much spare energy since you have mastered more jobs than normal, you will have tons of extra stat points at a lower level, making leveling up off a single energy bar exceptionally easy.
If you do not have an energy account yet, it's certainly the perfect time to make one!
As part of the fan bonus, players who log in March 30th or March 31st will receive the "Heavy Hand" limited edition loot item, which is a has 43 attack and 23 defense. You get it just for logging in.