Sitecore Gyan : Day 18

In Sitecore, By default all the codes runs in the security context of the context user.
And if user who doesn't have read access and wanted to perform task on the code then use Security User switcher or Security disabler.

using (new Sitecore.SecurityModel.SecurityDisabler())
{
//put the code here
}

Sitecore Gyan : Day 17

Admin can increase the number of allowed users up to 24 hours even if your license does not include these additional users. Because license agreement regulates the maximum user count.  And if you use this functionality too often, this can be a breach of your license agreement and Sitecore can charge you for the extra users.