Never heard of gift list poems before reading this thread and the ones described do deserve to be thoroughly mocked.
But to each their own. I don't see the problem with gift lists so long as they are inclusive, i.e. have prices starting at under a tenner. Also, unless your guests are passing acquaintances they will surely want to get you something the same way that that you give them gifts to mark special occasions in their lives.
DH and I included a list of 'items' towards our honeymoon. These ranged from a fiver for romantic bath gunge to £100 for a night's accommodation with varying prices in between for stuff like a picnic lunch, a day's car hire, evening meal, attraction tickets etc. We then included a picture of us enjoying said 'item' on honeymoon in our thank you cards (including one of us standing by the hire car while it got repaired
).
It was clearly stated as optional, guests mixed and match to suit how much they wanted to give and we got loads of positive comments on the idea. Many people also went off list and we got some lovely gifts of champagne, photo albums, a personalised clock, champagne flutes and a Zorb ball experience, all of which were also very appreciated.
I think that if you don't want physical things or you like stuff from a variety of shops, asking for money makes life simpler for those who aren't sure what to get you. If you know the person's taste get them something else you are sure you'll like. If you don't want to/can't give them money or anything else then just give them a card. I'm sure they won't mind since the important part is that you share their celebration. And if you don't think they'll see it that way then why attend the wedding of such greedy ungrateful shitbags in the first place?