What use are media-sharing sites for communities?

Some communities open accounts on media-sharing sites, such as Flickr for sharing photos, so that members can share photos, videos, and maps. This provides a simple way to document community events or to collect resources relevant to members. In other communities members use their own individual accounts and a common tag to share memories or resources. Sharing through a common tag means that individuals can share their photos, videos etc. across multiple communities.