Never thought about serving the dutch content on .com and not .com/nl Just because I find it looks strange, and I am more a fan of multilingual SEO with .nl, .de and the .com for English. The reason why we have subdirectories is because of the links, rankings etcetera. Maybe in a existent situation Dutch language on .com isn't that strange (if I look at it in an other way).
Well thanks you've helped me sofar, I will ask on Dutch communities before I'll decide.
Cheers!