I have a lot of "virtual" extensions that I don't need to (and would rather not) show up in the FOP. I've modified retrieve_op_conf_from_mysql.pl such that any extension that starts with FAX will not show, but it's kind of unwieldy (I have to name things FAX that have nothing to do with fax.)
It was a simple matter of making the change:
#$statement = "SELECT description,id,dial from devices";
$statement = "SELECT description,id,dial from devices where description not like 'fax%'";
Of course, the correct way to do this would be to have a boolean field in the DB "show_in_fop" and a "Show extension in the Flash Operator Panel?" check box in the extension page -- I'd do this on my box but I'm concerned about making database changes that would lock me into the version of FreePBX that I'm running.