etiquette moment

If someone sends you a terrific (or even mediocre) invitation to a bridal shower (or any event at all) with a really simple (or slightly complicated) way to RSVP for said event, RSVP for said event. You could write something like "My name is Kate Anderson. And I WILL be attending Jessica Tippet's bridal shower on Wednesday." or "My name is Becky. I'm not able to come on Wednesday. Could I drop a gift off at your house sometime before it? Call me!" or just "This is Jenny. I'm not coming." See, I just wrote 3 in like 1 minute. It's really really easy. You can be all business, or add a touch of personality to your response. It's entirely up to you. And it's incredibly helpful to hostesses that have never thrown a bridal shower before and have no idea if 200 mini cupcakes will be enough. I wonder if it's all my fault. I wonder if I've alienated older guests by only listing an email address? And underestimated younger/hipper-than-me guests that thought I was talking about this? Or maybe people thought I just still had seattle on the brain? And then there's the issue of 1/3 of the invitations being picky and wanting 17 more cents to go the 2 miles to the recipient and taking forever to come back to me and let me know that they need 17 more cents. I know, we're young, we hate commitment, we're indecisive. I understand that all too well. But seriously, just guess. Or be the first on the new trend of saying what you're going to do and then doing it. i know, it's revolutionary, give it a second to set in. (Can you guys tell that I'm a little nervous about this shower thing? It's just like a mixer? It'll be fine?)