Why do we have to imagine and then speculate from there? This is trivial to inspect.
It's 1.34mb on disk uncompressed but still minified. The copy Twitter is hosting right now is 1409121 characters minified but uncompressed. I have to assume the 4mb mentioned is output from some middle step (closure compiler output?) I'm not arguing the merits of that filesize, just that it's definitely not 4mb.
I ran into this problem last night and ended up looking at the script. File size is 4,129,653 bytes, on a single line. I had it saved to check out what the problem was, so here it is if you want to check it out yourself: https://dl.dropbox.com/u/24903613/hn/twitter-4MB-line.js
Interesting. The difference could be A/B testing or serving up different scripts to different browsers.
At a quick glance you can definitely see some differences between the different scripts we were served. For instance, in the one you were served there are some unminified portions that include the license notice for some of the code (easyXDM). In the script served to me there are no unminified portions, with everything being served on a single line.
It's 1.34mb on disk uncompressed but still minified. The copy Twitter is hosting right now is 1409121 characters minified but uncompressed. I have to assume the 4mb mentioned is output from some middle step (closure compiler output?) I'm not arguing the merits of that filesize, just that it's definitely not 4mb.