I'm curious about this, too. I was trying to figure out if it was on a 24 hour cycle, so I tried to take one this morning, expecting to get the exceeded daily limit message, since I took yesterday's about 1:00. But it let me take one. I hadn't cleared cookies or changed anything. Hope this wasn't a problem. When it let me into a survey on a topic I actually felt knowledgable about, I wasn't going to back out!