Pretty sure Amythest Schaber and her husband of "Ask an Autistic" You Tube fame fall under or near that category & they seem to be a wonderful, happy, healthy couple.
You can date someone as young as half your age plus seven years? It's no wonder that so many women feel that men their own age are too immature.
A 30 year old and 19 year old are in two completely different places in their lives. I'd just instantly stereotype it as the older one taking advantage of the younger one, because 90% of the time, that's going to be the case.
But if it works for some people, more power to them, and I hope they're happy.
Most large age gap couples I know are no more prone to such power issues than anyone else - it seems everyone only thinks of the "innocent 18 year old girl and the drug-using 30 year old man who served time for rape".
Oh, and those belonging to some conservative religions as that power play can be part and parcel of the belief system.