Others can see WPA?

Hi,

I have an 11g network at home that is WPA encrypted.
Can other people see that I use WPA? How can they
do that in such a case? Can they "check" my AP and see that is
WPA? How?

/

Anyone can sniff the packets in the air if they are within reach.
Sniffing tools would show encryption and given time and effort it could be
cracked.
But who would bother and why ?
Regards,
Martin