We put no more than 4 cubes on a 20A circuit, and with dedicated outlets for all printers, shredders and kitchenettes. Portable heaters are banned and the ban must be enforced; nothing trips circuits faster. Fans are OK as the load is negligible.
You could *probably* put more cubes on if you strictly enforce policy regarding extraneous loads, but limiting 4 cubes to a string strikes a good balance between economics and tolerance of plugging in unapproved coffee pots, microwaves, mini fridges, or whatnot. If you put more than 4 on a circuit or don't strictly ban space heaters, prepare for nuissance trips.
