So if i set up a dns server is it theoretically
possible to share wi fi with my neighbors but
they get my fake nameserver when they
try to get a dns name and i can spit
back a page that says something like:

"STOP HORKING MY SIGNAL"

?

Yes, provided they request a DNS address with their DHCP... if they manually specify DNS then it wont work.

Sounds like fun tho

Sounds like what I do in coffee shops. Course, it requires a bit of ARP poisoning first.

Then you can air-grep their traffic and replace whatever you want with...whatever you want.

Evil possibilities are endless, but I don't condone any of that!

Exactly. Such behaviors are just not condoned here so far as any of you casual surfers know.