Some websites such as MakeUseOf create non-bypassable popups when you have uBOL with Basic mode installed. Increasing the mode to Optimal will actually get rid of the warning and allow you through to the site without disabling ad blocking. For this reason, Optimal mode is a much better user experience when mass deploying to users in an enterprise setting.

Unless I'm missing something, it doesn't appear to be possible for admins to set the default filtering mode in uBOL when deploying. I'd like to request this feature to be added to the extension.