[rayiner]

No, "taken advantage of" does not require one party to be made worse off. That is not the way the phrase is ordinarily used in the English language.

[tesmar2]

Sure it is. If I am taken advantage of, I am not better off for it.

[mpyne]

You could be "better off", but still have been screwed out of being "even more better off". That's still being taken advantage of. Consider the legendary story about how Steve Jobs screwed the Woz.