There is a huge blog community where people have their own web page posting pictures of their gardens and other plant related events and garden they have visited. There are so many of them that they have at least a yearly convention some place in North America where they visit local gardens and talk plants. Many of those people lurk on these forums but they don't post.
Facebook has taken many people away from these forums. It is easier to post pictures. But you have to be very careful, people who don't like the plants you like take offense and say some out of the wall things in response to your defense of your plant. The trouble begins when the person responding is the owner of the group and kicks you off because you don't think bamboo is the worst weed in the world. Also Facebook doesn't seem to be as close a community as these forums. Some of these things happen on forums but it doesn't seem to be as much as on Facebook.