Q: I have sent invites to multiple ppl to my photo stream but no one received their invites. They are set up to receive invites to photo streams but it's still not working. Why?

I set up a photo stream that includes pics and videos and sent out invites. No one received their invites even tho it shows on my device that I have invited everyone. Everyone is set up to receive photo stream invites (I checked as we were all at the same event). I am using an iPhone 4. Has anyone else run into this problem?