very clever BUTTTTTT
if they wanna catch you, they have 101 ways to do that..it's only a
matter whether it's worth the trouble or not. technically you may
be able to evade but if they lay a trap for you and you are happily
using your method.. that's it.
anyway, if you haven't realise, there are already techniques out
there to detect/identify connected computers using spoofed mac
address/addresses.
one simple way to catch you would be as easy as once you are
detected using a spoofed address to connect to the network, the ap
alerts the admin and the admin monitors your internet activity,
seeing which websites or services are you using...the rest don't
have to say liao.. i think you know? lol. the next would be the
police approach you and handcuff u. 
