Though not, perhaps, in singling out Marc. I think there have a few too many somewhat coarse limericks across all the servers recently. We need a few rules of thumb here like:
- First lines ending 'Phuket' (or Nantucket, etc.) are never going to be funny
- Filth is always funnier if it's not signalled in advance.
Add your own.

(INJ) I agree more or less with your filth stance though if someone puts up an obviously dirty first line there is a strong temptation to carry on with the bawdiness. Unexpected filth is much funnier; years ago on PantsMC I put up the innocent first line:
"There was a young fellow from Streatham strettum", which was followed by
"Who chewed off his bollocks and ate 'em"
Aha, I thought, this is good.
The worst thing about too many of the current limericks is the lack of rhythm. I look at them and groan and think "Why bother?"

(INJ, Rosie et al.) Agreeing with the aforementioned points of lax scansion and over-active glands; but I would add that limericks which start with an obvious hope that they'll end up coarsely can be funny when subsequent moves elegantly sidestep it.
However, everything in moderation...

I like the sidestepping thing. It seems particularly English and I find I use it a lot here - especially as I'm in the lavisicous hotbed of the Netherlands and sometimes pretending to be more archetypally (sp?) English than I actually am seems to be the only way to avoid lowering myself to their standards. Oh. That means I am very English after all, doesn't it?
(And that rumour about the Dutch being liberal and easy-going? Don't believe a word of it. Most of them are Calvinists. It's a more conservative and male-dominated business and academic environment than any I have encountered before.