i've not been able to bribe any rebel armies and keep them, but i have bribed several rebel towns and kept them. and the interesting thing was, i expected the rebel cities to riot right away, since the happiness rating went to zero when i bribed it over, but, no riots and i didnt have an army in the town. i immediately built a temple and a peasant in the city and it brought the rating up enough that i got no riots. nice :) do that to a faction city and you'll likely get riots, but the rebels remained calm enough to keep the city.

K.