I guess it's time for pet peeves to be explored (e.g. "Hijacking Threads").
The ones that get me are the Topics that are originated with a Subject something like "... maybe ...." or "Yesterday I ....". With a meaningless Subject, you are forced to read the topic at least once to see what the poster was really talking about.

It's bad enough when a topic gets hijacked, but at least if the Subject is meaningful, you have a chance of knowing what it started out discussing.