Increasing loyalty through online communities. Applicability.

Continuing the previous topic, but separately: a

couple of general words about the applicability of communities to solve problems of increasing loyalty to a brand (or their group).

Communities will work where:
1. There is work on the retail market (B2C)
2. There is serious competition between sellers
3. The products offered are very expensive (that is, there is something for the seller to fight for).
4. The proposed products are difficult for an ordinary person to understand (otherwise the
site is not needed - there will be nothing to talk about ...).

Hence the scope of this approach:
1. Personal money (discussed).
2. Auto (strange, but there is still no sane site for just people,
I studied this issue recently).
3. Audio and video equipment.

Does anything else come to mind on the applicability? :)