@kirby @tk Probably to protect users from old filebomb prank which existed since the BBS times: you could upload a zipped file, which BBS then was supposed to decompress, the original file was the same character repeated millions of times, but in compressed form it was tiny. The BBS started decompressing the file, the hard drive filled up and BBS could no longer work in such borked up state.
So maybe it's something similar — to avoid files that could fill users' drives up from being transmitted, 2 gigabytes was still a lot at the time — three CDs worth of data, more than anybody would be willing to send over IM at the time.
Or maybe they have made it less than full DVD to prevent piracy — could be that :marseyhmm: Anyway, I don't think anyone would consider 2 gigabytes not enough then.