Bitcoin / Bitcoins / Crypto Currency

Anyone ever used or understand how the Brixton E-pound works?
http://brixtonpound.org/b-e-currency/

Allows users to pay for goods & services via sms txt message.
Appears to simply be a centrally held ledger which is updated upon receiving messages.

http://brixtonpound.org/wp-content/uploads/2011/09/A5-e-currency-leaflet2.pdf

Worried that it doesnt look very secure, as if the central ledger is compromised all my credit could disappear.

The ICT platform we are using, called ‘Monea’, is based on the Cyclos ICT platform. The ICT platform has been developed over a ten-year period by the Dutch NGO the Social Trade Organisation – and the current version is 3.5.6.