As an early adopter and one who likes sharing, I've embraced practically all these sites. I enjoy sharing and learning from the community, finding friends and shared interests. I like that I can explicitly use my NOOKColor to tell you I finished a book. I like that I can explicitly use Spotify to share playlists and my favorite tunes of the day, and I like that I can explicitly share from Google Reader to bring you the best from the Web I am reading. The human element, I believe, is an important one, where I signal to you what I find most valuable of all these things - what I have hand-selected for you and you specifically, to know.
There are two defining attributes of the services I've mentioned that I think are critical to enabling a positive user experience. The first is that the users who I am sharing with know just what they are getting into. They joined Foursquare to follow location updates. They joined Blippy to see purchases. They joined Last.fm to see music plays. The second, if the site is more of an aggregator, like FriendFeed in its heyday for example, is that filters exist, so I can avoid seeing your tweets, or your Foursquare updates, or your Flickr photos. Both of these ensure that the user, as the consumer, maintains control over what content they see and the publisher has a choice as to what they publish.
There is value in explicit sharing with selective audiences. There is value in the audience anticipating what they will see when they choose to connect with you, and in you having the opportunity to share what you want, when you want - an inherent, unwritten, contract, that if you violate by sharing too much, too often, or too off-topic, means your connection can be broken.
Spending a lot of time listening to mainstream social networkers, such as my wife, who is not quite as embedded as I am, I hear a lot about the minutiae of people's lives that go into these networks, and the resulting annoyances about such updates. Initial responses to sites like Twitter or Foursquare was typically skeptical, in terms of why people would want the small updates, seemingly unfiltered. Obviously, as both services have reached a good level of traction, thanks in part to power users and casual alike, there is some value to microsharing, and some are on the services constantly. But quality and filtering adds value - something I've obviously been focused on with my work at my6sense and constant testing of new products to make our social networking even smarter.
Sharing is going up. This is fantastic. Enabling more apps to share and people to connect is great too. But I hope quality and curation don't fall by the wayside.