Reg numbers being blanked out is a good thing because it helps to prevent them being cloned by nasty people and used on stolen cars to commit crime.
The trouble with Google Streetview though is that car thieves can still see the make and model of vehicles outside any premises and it can give them an idea of where to go for motors worth nicking.
In some cases their cameras have picked up things like TV's, hi-fi's, video's etc through peoples front windows.
Now you don't have to walk round an area looking suspicious, just pick your house on streetview and see if it's worth having a go at!!!