Joseph F. Smith said: “When messengers are sent to minister to the inhabitants of this earth, they are not strangers, but from the ranks of our kindred [and] friends . . . . In like manner, our fathers and mothers, brothers, sisters, and friends who have passed away from this earth, having been faithful, and worthy to enjoy these rights and privileges, may have a mission given them to visit their relatives and friends upon the earth again, bringing from the divine Presence messages of love, of warning, of reproof and instruction to those whom they had learned to love in the flesh.”
Angels are not only here to serve and protect us, in Hebrews, Saint Paul commissions us to do the same for them. Be not forgetful to entertain strangers: for thereby some have entertained angels unawares.
And since we can't tell who may or may not be an angel, wouldn't the wisest and kindest thing to do is to treat everyone as if they are an angel unaware?
I don't know about you, but I'm hoping to meet an angel today.