|Wireless has a lot of overhead to begin with unless you are foolish enough to run with no security. Consider wired to begin with. |
A normal hub is considered at full use at 30% utilization and a good switch at 70% (YMMV) Now you add in encryption it drops that a bunch. 20 people on a secure wireless would in my opinion be way too many if all needed anything more than text files. I'd limit it to maybe 5.
A good enterprise level switch can handle 20 users in wired. It might be the limit of a high dollar wireless in my opinion.
As above, network utilization along with backplane computation used to encrypt would tell the limits.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10