When I connect a social network to ICQ, who can see my activities?
When you connect to a social network, the feeds you receive are those that you are authorized to see on your various Social Networks (according to your friends' privacy settings). For example, if you are my friend on Facebook, and I publish something, then you will see it on your ICQ. Only you will be able to see this, and not any of your other ICQ contacts.
When you publish feeds, once you connect your facebook/twitter/flickr/etc to your ICQ, then anything you publish on those sites can be shared on the ICQ network. When setting up the service, you can select who on ICQ will see your activities.