There are several methods that you can use to perform a factory reset on your Bluefruit LE module if something gets misconfigured, or to delete persistent changes like UriBeacon or advertising payload changes, etc.
Once the module is powered up, if you hold the DFU button down for >5 seconds, the blue LED on the module will start blinking and the device will perform a factory reset as soon as you release the DFU button.
There is a FactoryReset sample sketch in the Adafruit Bluefruit LE library, which can be access in the File > Examples > Adafruit_BluefruitLE_nRF51 folder:
Upload this sketch and open the Serial Monitor and it should perform a factory reset for you:
You can also perform a factory reset by sending the AT+FACTORYRESET command to your Bluefruit LE module in your favorite terminal emulator or using the ATCommand example sketch. Make sure its in command mode first, then type in:
This command will also cause the device to reset.
On the back of the Bluefruit LE UART Friend board there is a test pad that exposes the Factory Reset pin on the modules (marked F.RST). Setting this pad low when the device is powered up will cause a factory reset at startup.