Is this possible—and, if so, how would I go about doing this?
That would depend on what you mean by a “small area” and how the items were stacked. If you were to throw 1,000 tagged pairs of socks into a cardboard cart in random orientation, you could probably use a handheld or fixed reader to interrogate all of the tags within a couple of seconds. It’s possible you might miss a tag or two, however, if one tag were blocking the signal to another, or if the antennas of two tags were touching, causing them to detune each other. If you were to shake the box or put a hand inside and move the items around, you would likely be able to read all 1,000 tags without any problem.
If the socks were on racks and one pair was in front of another, and if the tags were attached at the same place on each pair, it is likely that the energy from the reader would not reach the tags at the back of the rack. You would not be able to read those tags unless you used your hand to move the tags and create some distance between them.
—Mark Roberti, Founder and Editor, RFID Journal
Can I Affix Multiple RFID Tags to a Single Object? »