It's unlikely any sharpener is going to ruin your knife; at worst, they won't put the best possible edge on it. Your knife is probably just an inert hunk of steel. :)
Grinding too much of the edge does ruin the knife. Usually not the entire blade is hard enough to hold a good edge.
It's a fair point, but how likely do you think it is that any knife sharpening service is actually going to do that?