OMG I can't believe I'm going to stand up for Tink but presumably he was contemplating locking the topic because people were having a laugh, he was going to lock it because many of the recent posts were absolutely nothing to do with the title of the thread.
That would seem reasonable as people may click on the thread expecting to find comments about the smoking ban only to find that they have wasted their time. If I click on a thread entitled "Break-Ins", I wouldn't expect to find lots of posts about a bodily function or any other subject for that matter.
Of course I have been guilty of straying off topic on occasion, but surely there has to be a line drawn when the majority of posts having nothing to do with the original subject.