From the standpoint of someone who had to ask people to use common messenger among a team of people with varying team in the field operation at an event, bigge

From the standpoint of someone who had to ask people to use common messenger among a team of people with varying team in the field operation at an event, biggest issue I have seen with Google Hangouts (I guess this also applies to Facebook in that respect as well) is that there seems to be a bit of reluctance from people when they are required signing up to more "blanket" service, in this case, Google. I guess for some who do not use other Google services (especially when they don't use Gmail, YouTube, etc.) either don't want set up or show high resistance in setting up a new account with Google. Some privacy concern aside, many of those integrated services works great especially when they are used effectively, but I think the flip side is that those services tend to be "too heavy" for some people who just want to use it as a messenger and nothing else. (Actually, I wish they had an option like that.)