I think it is nice to promote bitcoin, but it is not essential.
To explain it I'll try to explain why bitcoin is usefull, even if it is used only by three people.
Let's picture too old friends, Alice and Bob, who spent a lot of time together during their youth. As friends, they help one another some times to times. Whether it is Alice lending her car to Bob for an evening, Bob watching Alice's kids, Alice helping Bob in repairing his bike, whatever.
Usually they help one another for free. They try to keep this relationship quite balanced. If, for some reason, it seems to Alice that she helps Bob more than Bob helps Alice, at some point Alice might be reluctant to go on being helpful with Bob. She might consider that she'd rather spend her precious time with her kids, her husband or whatever...
With time, Alice and Bob get to take a different life path, and they see one another less and less often. They are still friends, but now it is more and more difficult to convince for one of them to give help. Anyway, they don't really want to do it for free: they want some way to ensure that their overwhole relationship will be balanced.
So they start a basic monetary system. Just for the two of them. They use a dedicated book, and they write a number in it each time one of them give a favor to the other. There is no concern regarding centralisation, since they are only two people involved anyway: each transaction is necessarly seen by everyone in the "network". Although Alice and Bob have now a little bit "less friendly" relationship, at least it's more efficient now, and it's more adequate with their relationship that was becoming less friendly anyway. Had they stayed the best friends in the world, they would not have needed the book.
That the first thing to know about money: it allows collaboration between people who respect each other, but don't like each other enough to accept to give or help without expecting anything in return. Money is definitely not something for christians
Anyway, imagine now that Carl, an old friend of both Alice and Bob shows up. They all used to be best buddies in kindergarden
They would like to include Carl in their help/service/favor relationship network. But now, suscpicion can appear. Say Alice makes a deal with Carl: they both write the transaction in the book, but Bob doesn't have to be there. So Bob has to trust Alice and Carl not to do anything smelly that would eventually force him to return undue favors to one or both of them. In other worlds: trouble begins.
I think you get my point. Alice, Bob and Carl could just use bitcoin. It would provide them a reliable way to account for the favor/services they provide one another.
This is basically why I think bitcoin doesn't have to be mainstream. It doesn't matter if only a few thousand people use it in the world. It will still be usefull as a money, mainly because one of the service provided could be currency exchange, thus allowing the bitcoin community to interact with people outside of the bitcoin community, just because bitcoin would allow them to help one another to do so.
Say Alice wants to buy something in a shop which accepts only dollars. She has very little dollars because dollars mainly belong to banksters thanks to B. Bernanke. But she has bitcoins and the support of the bitcoin community. Some people in the community do have dollars. The more they are, the more likely it is for them to gather enough dollars to buy the stuff Alice wants. Alice will gain a favor if she gets those dollars. Such a favor won't be free: it will be measured by the bitcoins she will give in exchange.
What I am trying to say here is that currency exchange is really the most important service you can provide for the bitcoin community. We should focus on that, much more than we focus on promoting bitcoin (although promoting bitcoin is fine, but not essential imo).