I once committed to book a table of ten for a charity dinner / dance, a fundraiser for a hostpital radio station. Then I set about the task of selling eight of the places to friends. I got four couples to commit and we were set for a good night out. I trust my friends so I had no trouble paying for the tickets, then I would collect the money later.
One couple dropped out, I resold the tickets, a nuisance but no big deal.
Then a week before all four couples dropped out. They knew that I bought the tickets, but non of them offered to pay, and at such short notice I only managed to re-sell one of the tickets. The last straw was one of the couples pulled out the evening before the event.
I have never bought tickets to an event like this since, and I have never spoken to two of the couples, so called good friends, since.
When I say I'm going to do something, I do it, even if I regret the commitment at a later date, it's just bad manners otherwise.