If I go from product management into software development into some sort of technical marketing or sales role or even to certain types of consulting, there's a fair bit of overlap in the IT industry related to general knowledge of the market, practices, etc. I've changed jobs substantially twice and significant training to transition was never needed at all.
And, sure, if you want to change to a completely different area with much less overlap, that's not to say you shouldn't do so. But I certainly couldn't walk right into an unrelated engineering job at this point even if it were related to undergraduate coursework. In fact, it would be probably be easier for me to do a software job today even though I did essentially no programming in school.
