In a word - NO. Don't do it. Why do you need more onesies, blankets, bottles, a new car seat, high chair, etc.? More importantly...why should other people buy them for you. AGAIN? You're the one who decided to continue with the most expensive past-time (child raising), so why must the pocketbooks of your friends and families suffer?
Is it surprising to learn this custom originated in the United States? I understand, and fully support, baby showers for your first baby (but really, just have one. You really don't *need* three unless it's purely for geographic reasons), although, like wedding showers, I find the whole "unwrap a present you picked and put on a registry and then exclaim 'Oh my gosh I love this...'" very odd. I mean, you picked it out. You basically told us to buy it for you. But I cannot get behind a baby shower for your second or third child. Just because you had a boy first and are having a girl second does not mean you need to have another baby shower. I'll let you in on a little secret...baby girls can wear blue! It will be okay! It won't make them grow up socially stunted or prevent them from making the cheerleading squad.
I do want to point out the following:
1. Adopting a baby? Yes! Have a baby shower (if it's the first child in your family). Just because it didn't come from your womb does not mean anything. It's still your first child! So exciting!
2. If you had a baby in 2000, and sometime around the time your first child is entering college you get pregnant again...okay. Maybe. I'm sure they'll find poisonous paints/toxins/etc. in all the baby stuff on the market now. Or you didn't hang on to anything, because you thought you were done.
Let's all (meaning the two people who I force to read this site) agree to boycott baby showers for anything other than the first born. Only through activism will we end this ostentatious trend!