The only webservice I pay for is DabbleDB. Dropbox I can live with the restriction, but you absolutely need a database when you need to track a large amount of items.
I'm REALLY suprised that there are not cheaper alternatives to DabbleDB - if there had been anything a bit cheaper or a bit more ajaxified, I'd have gone for it.
Also, the main reason I don't pay for dropbox is that you need to pay for EACH user! So at just 5 users I'm paying $50 a month. That's crazy wasted money!
eh incentives. we all do this to some degree on a daily basis. e.g. downloading your favorite song for free instead of paying .99 for it on itunes, etc.