When you display a tweet embedded in your page, you have to display it exactly as they do, which takes up a truly ridiculous amount of space and is intentionally prohibitive.
And as a sidenote, Twitter would very much prefer if the API would just disappear, as they get non-linear benefits from users going to twitter.com instead of accessing its services through a third party. Internally, it is spoken of as a liability.
I doubt that their API is spoken of as a liability internally because, if it was spoken of as a liability then Twitter.com itself is a liability. Why? Twitter.com itself is powered by their API[1]
It is spoken of internally as a liability, and the executives want nothing more than to get rid of it for many reasons, not the least of which being their current investors care only about user numbers, and don't seem to count third-party users.
And as a sidenote, Twitter would very much prefer if the API would just disappear, as they get non-linear benefits from users going to twitter.com instead of accessing its services through a third party. Internally, it is spoken of as a liability.