Please check this one out and vote it up.
The issue is that calls like llGetParcelDetails and llScriptDanger which are frequently used to check if it's safe to move into (or over) a chunk of land can't look across sim lines. It would be very nice if they could at least see the details of the parcel that sits just across the line.
If you've ever been in a vehicle that crossed into another sim and found yourself getting bounced off your vehicle (and maybe losing the vehicle), please give this a vote!!
http://jira.secondlife.com/browse/SVC-221