To continue with the general question of how many people. I recall I probelm I had with SBT (older version 6.35) that did limit the number of users. The limiting factor turned out to be how long a record lock took. SBT used a single file to track transactions (SYSDATA.DBF). Almost all computer generated keys where stored in the file. As a result we started getting delays where the user had to wait for the locks. Well somewhere over just 120 users the delay was just to long. The server at the time was a sun (the one of the fastest back then). They ended up using different software.
