I have an honest question- why is it tacky if someone else throws you a shower for your 3rd, 4th, or whatever child? I'm not understanding how it's tacky if YOU didn't ask for it...
I DO however think that it's tacky to throw your own shower, even if it's for your first child. I feel like it's asking for a hand out.
That being said, I've had 4 "showers". With DS #1, I had 1 shower and only THREE people showed up.

: With DS #2, MIL had a shower for me entirely too close to my due date so I was extremely uncomfortable. StepMIL had a shower for me after the baby was born (He was only a few weeks old so I was in NO condition to go to a party but did anyone ask me?? Of course not) bc her family doesn't get along with MIL's family (they did the graduation party for DBF the same way. They separate everything) My mother couldn't attend either party and badly wanted to so she threw her own but she lives in NY so I couldn't attend lol. She video taped it for me and she and her guests had a BLAST. My mom came to visit and brought gifts from the shower with her. So I had 3 showers with 1 kid and I didn't ask for any of them. Tacky? No. I think emphatically not.
With future children, I plan on throwing my own parties but they will be welcome baby parties to be thrown when *I* feel like it. The invitations will have a nice little blurb reading something about how gifts are NOT expected or necessary but if they'd like to bring a gift, that's fine. It's going to be to celebrate the baby though since well, I've got tons of stuff and don't really *NEED* anything. I had blood pressure issues with my last son when people came to visit me so we'll see if these welcome baby parties are even possible when the time comes.
I still don't think it's tacky if someone else opts to throw you a party. I honestly don't understand how in the world someone could consider it tacky unless you threw it for yourself. I mean like I said, if you didn't ask for it then YOU didn't ask for gifts. I agree thought that 6 page registries are tacky! BLECH