In this short demo, I copy various pieces of text from Twitter.com in Safari 5.1.3 on Mac OS X 10.7.3. You will note that I have a bad habit of repeatedly hitting Command-C when I only need to press it once. I can copy any text except when the selection ends at the last character of the linked text for a shortened URL.
While I can copy the URL of the link using the context menu, that will always be a t.co link. (This is not shown in the video.)
If I want to copy the text of a bit.ly link so I can paste it into the address bar and suffix it with + to see the link's stats, I can't.
I follow @imAK48, but Twitter showed me a tweet of his and the button was labelled "Follow" which indicated that I was not following him. I never clicked follow button in this video.