K.P.
Vinegar is an acid, so it would weaken bones... if submerged for days on end! A couple of little gherkins once-in-a-while isn't a big deal. You may want to avoid the every day treat b/c there's a lot of salt and sugar in the brine.
I love how some people take a simple science fact and attach it to something completely illogical. My mother-in-law swears that milk consumption can cause ear infections! Yes, excess mucus can result in ear infections, but simply drinking milk doesn't!
Crazy, but at least you know they care!