<p>What is the purpose/meaning of the Version property on a FormsAuthenticationTicket?</p>

The
docs
are less than enlightening on this one, though the default version number did change
from 1
to 2 with ASP.NET 2.0.
Reflector didn't turn up any interesting uses of it either, other than keeping it alive on renews. My guess is that it's for "future use".