The document
http://wiki.postgresql.org/wiki/VACUUM_FULL says:
VACUUM FULL, unlike VACUUM, tuples data that has not been deleted, moving it into spaces earlier in the file that have been freed. Once it's created a free space at the end of the file, it truncates the file so that the OS knows that space is free and may be reused for other things. Moving in-use data around this way has some major downsides and side-effects, especially the way VACUUM FULL does it. There are better ways to free space if you need to and better ways to optimize tables (see below) so you should essentially never use VACUUM FULL.
PgAdmin does not give the user a comparable warning when it goes to execute a VACCUM FULL. Given the potential problems with the FULL option, would it make sense for PgAdmin to issue a warning to this effect?