Most organizations really want a big following, not a community.
A following is an audience that interacts with you. A community is an audience that interacts with each other.
A big following suits organizations that sell commodity, non-sociable, products. Coca-cola is a great example. Huge following, but no community. Likewise nearly all bloggers have followings, not communities. Many politicians, authors, salespeople also have great followings. Big followings are built by engaging with as many people as possible, creating great content, promotions/discounts, coverage in top blogs etc...
A community suits organizations that sell sociable and highly engaging products/services. Communities are small, highly engaging and exclusive. Software products often benefit from communities. As do manufacturers of niche products (e.g. Samurai swords, metal detectors etc...). Communities are built by interacting with a small group of people, initiating events and discussions that foster interactions between this group and soliciting ego, time and emotional investments from members.
You only need a community when your audience has a desire to talk to each other and when there is a benefit (to the audience!) from talking to each other. Very, very, few organizations fit this criteria. Perhaps as low as 1 in 10.
If you hope to build a community with a following approach, you're going to be disappointed. If you hope to build a following with a community approach, you're going to be even more disappointed.
Most of the time you're better off trying to build a big following. Just don't mistake the two.