I have the same problem with Pidgin 2.6.6 in 10.04 (and Pidgin 2.7 in Fedora 13). The notification area slowly grows as I have Pidgin configured to only show the icon when new messages arrive. You can also make it grow quickly by repeatedly turning on and off the setting for always having an icon in the notification area (or system tray, as Pidgin calls it...).
I have the same problem with Pidgin 2.6.6 in 10.04 (and Pidgin 2.7 in Fedora 13). The notification area slowly grows as I have Pidgin configured to only show the icon when new messages arrive. You can also make it grow quickly by repeatedly turning on and off the setting for always having an icon in the notification area (or system tray, as Pidgin calls it...).