<p>When adding a reference to a project I sometimes see the message...</p>

<p>"The Target Framework version for the project is higher than the current project Target Framework version. Would you like to add this reference to your project anyway?"</p>

<p>I understand what the message is indicating but can anyone explain what issues might arise from saying 'Yes'?</p>

Suppose you build an application where the exe targets 2.0, but some library targets 3.5. Someone with a .NET 2.0 machine looks at the main project and thinks they can run it - after all, the application targets 2.0, right? When the library is first loaded, they'll get a nasty surprise...