@NotLarryEllison, security is a really great question to bring up early on. I'll post something on the team blog http://blogs.msdn.com/b/lightswitch/ regarding security during our beta 1 timeframe.

A short summary for now:

LightSwitch supports varying degress of security, including transport level security between the client/mid-tier and mid-tier/database, SQL logins for data access, and client logins for accessing the middle tier. On top of platform level security, LightSwitch also supports access control business logic. The application can define Permissions that are associated with Roles. In the LightSwitch business logic, you can enable/disable access to data, screens and commands by testing whether the current user has a specific permission.