I have long been suspicious of certain whois tools "monitoring" names typed in and then stealing the name for them selves if it is free.
A couple of years ago I ran a whois on a list of possible domain names for my new site and found a really great one was free, two days later I went to purchase it and it was gone! Well apart from pissing me off, it made me very careful now and every time I have purchased a domain name since I have deliberately waited until I am ready to purchase to go through and find a domain name that is free and get it immediately.
The problem is that sometimes you may want to find a few free domains and give your self a week so you can think about which is best.
1) Is there a law against sites stealing your domain name ideas?
2) Is there a trusted site that is perhaps government run?