I get a bit cynical about blessings at times, I suppose because there could be an air of superstition to them; but blessings do seem to satisfy some primal need. Georgiansilver's example of the blessing of a ship is a good example, and fishing communities often bless the entire fleet each year, asking for a good catch and protection from harm. Many cultures bless new homes, and some bring food for blessing before traditional feasts like Christmas and Easter. Mudcatters post "good thoughts" and birthday and celebrity obituary threads, which I suppose are a form of blessing. You could call it blessing, or you could call it well-wishing.
Can't see where it does much harm, although I think that people get carried away with it at times.

-Joe-