Most of us don't like our whois information being displayed in public. Whilst I've never done it, I know quite a few people that put down fake information.
What you probably didn't know is this is grounds to have your domain name deleted and some sort of legal action for something like fraud taken against you.
People can actually report false whois info here:
ICANN | Whois Data Problem Report
In my opinion a better solution for people is to use services like DomainsByProxy or WhoisGuard that will put their details in place.
Some registers will give these services away for free with registrations, but others may charge a tiny fee of around $2.