3-4 (each on different walls) makes sense to me.
Our house is 103 years old, but the owners before us did wall and electrical work upstairs. We have an average of 2 outlets per wall! In the bedroom we use as an office, it's a nice feature, but most of the others are not used.
You can imagine how nice it was, though, since we moved from an apartment with only 1 outlet per room, and none of the outlets had the third, grounding prong. DH and I each had computers, monitors, we had a printer, a fax, answering machine, a TV, a VCR, a DVD player all jammed into the one sad living room outlet, daisy-chained with extension cords. Not good!!!!!!
Anyway, yeah, 3-4 per room would be good and not overkill.