Need another watering can to irrigate those crops on your highly-profitable Facebook farm? Soon you may be able to boot that expense directly to your monthly mobile tab, just as you do with other necessities, like ringtones and emoticons. The social networking site is working with carriers to streamline billing, eventually enabling Facebook users to pay their app dues along with their monthly phone bill. Naturally, this is a win for developers, since eliminating the need to pre-purchase Credits or enter card information will result in an increased number of impulse purchases -- and let's face it, there's no line item for FarmVille
