Personally if I were a guest I'd be PO'ed if I started getting facebook or email or text messages asking me if I'm coming or not and the RSVP date hasn't even come and gone yet. I ALWAYS RSVP but sometimes it is last minute. I sometimes need to get a babysitter and many times don't know if I need one until a week or so before the time I need one.
Wait until the RSVP date (maybe a lot of people are like me and wait until last minute to RSVP) or maybe a lot are like many of our wedding guests and just don't RSVP so they need to be called. It is your hostess' job to call/email/text/etc. them not you. Obviously if they contact you instead of the person on the invite you can let the hostess know...but otherwise you just need to stay out of it and relax.