The same "exploding offers" are prevalent in the job-seeking world as well. I fell victim to one accidentally: I was trying to happily accept a job but the acceptance deadline detailed on my offer actually expired the day after I received it in the mail. At the time I thought it odd that the company was in such a rush to get a response from me that they couldn't give me a week or so to think about it. Then I got there and found out very quickly why they were pushing me into taking their offer. Three weeks later I had quit. I'll never take an exploding offer seriously again and commend YC for being gracious and flexible in their process.