marktplaats indeed has no obligations for a seller in the way of selling it to the "winning bid"
usually sellers on marktplaats are dutch, and when they see a foreign bidder (no offence) they preffer a fast pickup by a local guy instead of someone outside of the country.
so yeah, there are sellers that use the Ebay practice on marktplaats, but they dont have too.
I also have a bad experience once, i was after an item, and i called the seller, i even made a appointment for pickup, and the night before the pickup day i received a email that the item was gone to another buyer, even though we had an agreement..
in that way marktplaats sucks..