I don't get why AT&T would agree to pay 4 billion if the deal falls apart. I understand some insurance maybe a little some legal fees and some other things that AT&T should pay for I get that. But 4 billion. that's crazy. I mean I don't walk into a Store and say I want to buy this but if I don't I still owe you 10% of the price i was going to pay. That's just stupid, and AT&T gets Nothing for that 4 billion. Talk about having money to throw away.
Every single merger has such a fee. There are many reasons for the fee. One of the reasons for the fee is to ensure the acquiring company is acting in good faith and not trying to damage the company that is being bought out. Another reason is to recoup lost revenue from customers and investors fleeing due to uncertainty.