To be fair, I didn't know if the movie was going to be completely sung through. The trailers definitely gave the impression that there was more dialogue than there actually was. I can think of at least 2 bits from trailers (Marius asking Eponine "who's that girl?" and her not singing the response, and the bishop saying "I know who you are. You're Jean Val Jean,") and neither of these were in the actual film, so if you've never seen the stage show, I can see why some people wouldn't realise. Like I said, based on the trailers, I expected a lot more dialogue than we actually got.
Not a complaint, btw. Just an observation.