This depends on variety of factors.
1 - How fast is your internet speed? If you are connected to ADSL via phone line, your internet speed is probably not fast enough for sharing it with others. But if you are connected with broadband internet (Coax Cable or Fiber Optics), your internet speed won't be a limiting factory, specially if you have fast upload speed (+100MBsec).
2 - The nature of usage: If the people you share your Internet with all start watching high quality video at the same time, there won't be enough bandwidth for everyone. On the other hand, if the Internet traffic is limited to web browsing or messaging, 100s of users can connect at the same time.
We recommend limiting the total number of users under 20 so that the overall incoming traffic can stay undress certain censorship limits and overall stay under the radar as much as possible in terms of traffic load.