It was most definitely "hogging" it. There was no free RAM left and the pie was nearly all red and yellow. I was also running Photoshop, Flash, Safari, in addition to the usual suspects. The reason I bothered checking Activity Monitor was because things were clearly running sluggish, and the trustevaluationagent was by far the biggest RAM eater.
Anyhow, it seems to have been caused by that SimplenoteSync script that I was trying to run every 5 minutes to sync Simplenote with NotationalVelocity. The past two times I saw that trustevaluationagent was in Activity Monitor and gobbling up RAM, I also saw that NotationalVelocity was giving me warnings that some notes had been deleted from my hard drive. I'm pretty sure the two were related. Since killing the script, things have been fine.
So the question remains, what exactly does "trustevaluationagent" do?
Erik