If you are the first person to write a bot to automatically submit entries, you could submit most/all of the allowed 10 million entries.
OK, maybe your IP would get banned, but what if you have access to a botnet and, therefore, lots of IP addresses?
OK, maybe they have a captcha, but what if you trick your botnet victims into filling in the captchas during their normal web browsing sessions, by pretending to be a google bot-detection page?
OK, so you win, but the address is a random address that isn't yours. How much would you have to give the person whose address it really is, to pretend you live there? Half? Still not bad.
OK, maybe your IP would get banned, but what if you have access to a botnet and, therefore, lots of IP addresses?
OK, maybe they have a captcha, but what if you trick your botnet victims into filling in the captchas during their normal web browsing sessions, by pretending to be a google bot-detection page?
OK, so you win, but the address is a random address that isn't yours. How much would you have to give the person whose address it really is, to pretend you live there? Half? Still not bad.