Brian, as far as I can tell, it's complicated and seems to vary a bit state by state. In some states, the service charge must go to those who provided the service; in others, it can go into general restaurant revenue but in that case the restaurant must pay their servers the federal minimum wage ($7.50?), not the tip-exception rate of $2.13/hr.
IRS regulations that went into final effect this year require that the service charge that goes to employees be considered wages, and taxed accordingly; meaning, the server gets the money but it's taxed as ordinary wage income.