A great piece in Sundays NY Times outlines the growth of soft earmarks in Congressional bills. Basically, a soft earmark is less recognizable and is difficult to identify because it doesn't ask for specific dollar amounts. The ask is more non-descript. It camouflages itself as a suggestion or recommendation. Thus soft earmarks are more able to slide by unnoticed compared to hard earmarks.
Their total cost is not known. But the research service found that they amounted to more than $3 billion in one spending bill alone in 2006, out of 13 annual appropriations bills. And the committee that handles the bill, which involves foreign operations, has increasingly converted hard earmarks to soft ones.

“This shows that even though lawmakers now have to disclose their pet projects, we’re not getting a full accounting of earmarks,” said Ryan Alexander, director of Taxpayers for Common Sense, a group in Washington that tracks earmarks. “We may just be looking at the tip of the iceberg.”
The danger in soft earmarks is that there is no process in place to bring them to the light of day, and even if there was, it would be difficult to figure out all of the details as they are by their nature, vague.

Some folks have started a spirited debate about earmarks on our discussion group. Join the discussion so we can hear your $0.02.