Does Bluetooth Smart require pairing?

If you want to receive data from the beacon to the device that's outside of it's advertisement, then yes it must be paired. BLE/ BtSmart currently is either advertising or paired. For this reason it can only support one connection at a time. This may change.

Whether or not you've paired with it in the past, previously discovered it (aka have its advertising packet stored) or not is irrelevant. Again this is currently.

My question would be what data are you wanting to transfer from the beacon to the device, or vice versa. You may not nred to pair. Pairing reduces battery life and makes your beacon undiscoverable, reducing it to a 1 to 1 interaction. Both undesirable depending on your application.

--

This is a bit of an open question.  As it stands today there is a pairing profile called "Just Works" under the Secure Simple Pairing of Bluetooth v2.1 and above can do this in theory.  However the implementation of this pairing system is largely on the device manufacturer.  As more use cases are established systems like "Just Works" will become quite common.

⦁ Just works: As implied by the name, this method just works. No user interaction is required; however, a device may prompt the user to confirm the pairing process.

--

There are two main mechanisms in Bluetooth Smart to transfer data

The first is via broadcast/Advertisement. In this case, a broadcaster sends what's called an Advertisement packet with data. Many devices can receive this data at once, but they cannot respond in this mode. A Scan Response can them provide some more information.

The other method is with a connection. When two BLE devices connect by exchanging some connection information, they can transfer data every time a connection event happens. This can go both ways (the only way for both of them to talk to each other).

What you're talking about seems to be via broadcast. In this case a phone or another Central device can capture the packets sent by multiple devices (such as beacons).

--

Bluetooth Smart offers a paired and a non paired communication. After pairing the paired devices are not visibale anymore. You will get a non visibale, secure communication link between a master/central device and a slave/peripheral device. 
Bluetooth Smart offers a broadcasting of data as well. A  Broadcast message could be the daily menue at the cantine in university, the weather data or the ID of a beacon for indoor locating like listed here:
Bluetooth Low Energy Beacon - Indoor locating
World’s first combined Bluetooth 4.0 / ANT beacon evaluation kit for indoor positioning

--

It does not require pairing, but...
The Bluetooth Low Energy (Bluetooth Smart) protocol does not require pairing. However, Microsoft's implementation in Windows 8 for example does require pairing. Android's implementation does not require pairing. So it's up for every OS/manufacturer to decide on their own implementation.

--