Comment 1 for bug 574553

I can confirm this on lucid and maverick beta.
telepathy-salut need the memory of the file being transfered (it grows as much as the data that has already being transfered).
The CPU consumption also increase when the data that already send increase and that leads to very low speed at the end (CPU limited).

I'm currently at 90% CPU (Intel C2D 2,3Ghz) et 900kb/s (currently limited by the wifi connexion) after 350Mb have been sent.
After 450Mb being sent, the CPU is a 100% (one core) and the speed is 750kb/s (the CPU limits now).

Notice that the trouble only happen at the sender's side, not the receiver's side.