Steelers Depot explains why the Steelers are likely to receive just one compensatory pick, at most, in the 2012 NFL Draft. The Steelers lost unrestricted free agents Matt Spaeth, Nick Eason and Keyaron Fox last offseason, and compensation for those losses is based on those players' data from last season.
Compensatory picks are awarded by using a formula based on salary, playing time and postseason honors and is also weighed against any unrestricted free agents signed from other teams in addition. The formula that is used to determine those picks was developed by the NFL Management Council and has never been made public.
Spaeth, Eason and Fox were all role players in 2011, so it's unsurprising that the Steelers wouldn't get much. In fact, they might not get any at all. (If they get one, it would probably be for Spaeth.) Steelers Depot notes that the 2013 Draft will likely be a different story, since William Gay, who just left for the Arizona Cardinals, should get a bunch of playing time in 2012.
For more on the Steelers, check out Behind The Steel Curtain.