At first the idea of every device having a public IP address seemed like a security nightmare to me... but how easy is port-scanning the IPv6 Internet? If the addresses are sequential it obviously won't make any difference (you just need a list of ISP address ranges, e.g. from BGP, and start from the bottom), but maybe we can hand out addresses some other way that will make it very unlikely to find another device on the Internet? Slighly related: is the last bit the reason why we still haven't met any aliens?