Prior to their communist revolutions, both the USSR and PRC were actually practicing something not very different from feudalism. In fact, one of the reforms of the last Tsar was to unbind (legally, if not in practice) serfs from their estates.
Serfs were freed in 1861[1]. A year before slaves were freed in the USA[2]. By Alexander II - the grandfather of the last Tsar.
[1] http://en.wikipedia.org/wiki/Emancipation_reform_of_1861
Totally unsurprising, given that their "communist revolutions" were revolutions in name only, and happened in conditions Marx had spent decades explaining why would not lead to successful transitions to socialism, much less communism (first, as far as I know, in "The German Ideology", 1845, Part I, section A, 5: " And, on the other hand, this development of productive forces [...] is an absolutely necessary practical premise because without it want is merely made general, and with destitution the struggle for necessities and all the old filthy business would necessarily be reproduced").
Both the Bolsheviks and the CCP quickly re-established near feudal structures in response to opposition or failures - soon only the titles and names were different.