I've been to a couple of showers where the guests were asked to address their own envelopes for the thank you cards.
In my mind, I rolled my eyes a bit, but, on the outside, I cheerfully addressed my envelope because I'm a "get along" type of girl. I'm not going to write "Lazy Bride" or anything else like it on the envelope, & I'm not going to refuse to do it on principle. I'll write my name & address & then go on w/ my day.
But it's not something that was done at any of my showers (wedding or baby).
And, while I don't think it's the worst thing ever in the world of manners to address my own thank you envelope, I do think many etiquette experts would probably frown on the practice.
However, I'm just happy to receive a thank you note - whether it's been addressed by me or not. What has happened to writing thank you notes?!
I was at a baby shower about 6 months ago & couldn't stay for the entire thing, so I wasn't even there when the gifts were opened. I still haven't received a thank you card. But I'm not sure why I was expecting one. Two years ago, I attended the girl's wedding & never received a thank you card then either.
But she's not the only one. The daughter of a lady w/ whom we used to go to church had her first baby. She didn't have a shower, but I gave her mother a gift to give to her daughter. Who knows if she actually did? Because we never got a thank you - verbal, written, sent via her mom, message on FB, anything.
There have been a few other occasions recently as well at which we've given a gift, but never received a thank you card. And I'm not talking about birthdays or Christmas where you're generally thanked at the time the gift is opened, I'm talking about weddings & showers. At the very least, I want to know that the person received our gift & that it wasn't lost somewhere.
So, if having the guests address their own thank you envelopes will help the gift receiver to actually write & send her thank you cards, then... whatever. Go for it.