This bug has affected me -- amd_64, beta 2 of Lucid.
My cpu graph was pegged ALMOST to the top constantly; I thought it was npviewer-bin, since that used to be a monster. After running Top, I found that Gwibber-service was using 85-95% of my CPU cycles. (single core, 3GHz P4)
I had one Twitter account set up in Broadcast accounts (assuming that's gwibber?). That was it, though.
After killing gwibber-service, things have returned to normal.