CrazyNutJob, dedicated in his search for truth, answered:
I called 1-800-829-1040 and pressed 1,4 on the menu. Mark at the IRS strongly recommended against it, but told me that they probably would.
I guess that answers that. Please don’t get yourself arrested on my account.
You provided us with a little educational amusement at the end of the workday. To elaborate beyond the 140 character limit: I first tried Google, and looked through the various IRS FAQs. I found the IRS question line on one of the FAQs. After navigating the menu, I first spoke to someone who wanted to know how to direct my call. I told her that I had a question about paying taxes by check. That directed me to Mark, who was quite pleasant to talk to. I told him that I was aware of the fact that I should make my check out to the “US Treasury,” but I was wondering if they would still cash a check made out to “Uncle Sam.” This elicited a bit of laughter. He suggested the “Department of The Treasury” as an alternative. I informed him that I probably wouldn’t actually make a check out to “Uncle Sam,” but was really quite curious if they would cash such a check. He once again cautioned against doing so, but then admitted that they probably would. I’ve never had reason to call the IRS before, but I must say that they were very courteous and helpful (even directing my call was painless).
As a bonus, it appears that I’ve picked up a tumblr follower from the experience.