Ok.
1. IP addresses are not like "Here is your house number and street address in number form" they are very very relative.
2. Whenever you JOIN a sever, your IP address shows up in the console. Whereas if you START a sever, no one can see that IP address.
3. In a sever of your very own you have complete control. If your mom is sensitive to language you can add or subtract words from the Filter list and Viola, never have to see them again. Also, if someone comes into a sever that is not yours and begins to be a.. Butt-hole there is nothing you can do about it. In a server that belongs to you, you can get rid of these idiots by clicking 2 buttons. You have more control and can censor what ever you want.
Also, on top of Dig said, have you ever been to one of those sites and at the bottom it states
"Find girls in *Insert City Here*!
That is determined by tracing your IP address. If anything Blockland is Safer than the internet. (lol)