Humorous PAs
I think it could be quite easy to misjudge the 'crowd', and leave people with the same impressions as limpbiscuits.
For example, the whole 'Welcome aboard this flight to... Oh, were are we going again? Oh that's right, Melbourne!', must get tired if you fly a couple of times a week. In fact, it would get tired if you only ever flew twice in your lifetime! One guy i know of actually failed to see the humour in that exact PA, and genuinely thought the crew were unsure as to the destination, but we won't go there.
The scripted and prepared nature of most of the jokes just ain't funny. Afterall, most of the best humour is that which is spontaneous.