It's an over the top guilt trip.
"remember how I swapped for you... well seeing as how I did you that favour we could make it even if you blah blah blah and on and on..."
I told her once I couldn't swap with her as it was Tegans mums birthday and she went on about it for weeks.
( Maffers I flow kinda strange like Spina Bifida footprints, Mon 27 Apr 2009, 10:04, archived)

well that's just wank
when you get someone to swap always agree on the shift you'll do for them at the same time.
(Just Harry What should I put here?, Mon 27 Apr 2009, 10:13, archived)