99.999999999% of Labradors would rather slobber all over a burglar rather than jump for the jugular. They are not the best guard dogs. No where near as good as a Doby, Rottie, Shepherd, etc. Many Labs will bark, like all dogs, to show the tresspasser they don't like them, but after they get to know the tresspasser they are ok with them.
ok coming from someone who belive's there is such a labrador colouring such as silver

first ever dog that attacked my dog at obedience was a lab

dogs most likly to be rushed to the vets with stomach blockages (labradors)
cannot help themselve's will eat anything