Nice straghtforwards question.

I found this one easy to answer because years ago I wrote some code to detect undesirable blocking behaviours in a particular system that had a couple of extremely buggy apps with rotten embedded SQL and kill off the root blocker; this was actually safe given the overall system design, although it wasn't a desirable things to do things, and worked fine for some time; then along came SP4 and it started killing things too often - which turned out to be this problem. Very easily fixed once I discovered that this was expected behaviour, but a week or so of very real worry before I discovered what was going on. (Of course we planned a rewrite of those apps, including restricting them to use only stored procedures, no other db access, but it took a long time to get a plan approved and a long time to get a decent implementation; but eventually that block detector ceased to be needed.)