Keep in mind how Google's database works: These notes can only be found if there is a link to them on a page already in their database. That means one of two things: Their profile is set so that Google can read it, and it scraped the link from there, or someone posted a link outside of Facebook to the note.

Its a lot like all of the private FTP sites you find in the Google database (Do a search that resembles * : +intitle:index.of +"last modified" +"Port 80"). While some of them may have been meant to public at one point, all it takes is one link pointing in for Google to find it and open it to the world.

*A note about that search: it returns some place in the realm of ~12 million results. A massive number of those are intentionally open, for thins like open source projects. You'll have to append something ridiculous like -inurl:(com|org|net|edu|gov|uk|fr|gr|www|jp|ftp|eu|biz|info|ww|ca|ac|ru|se|us|ch|ua|pl|ch|am|co) to even start seeing links to IPs, which I would guess have around a 99% probability of being someone's home computer that they put Apache on to make life easier, and then put a link some place so they could remember it.