I’ve signed up to play The Prague Network from the Livegames Network.  They;ve previously run something similar in Melbourne, Australia which looked interesting.   Played over 2 weeks, requiring an SMS phone, email and web access it could be fun.  But as ArgNet discusses, as it requires a subscription ($6.95) and a US address will it take off enough to be a success or are these too high a barrier?
Many other ARGs have either been run for fun or as part of a larger marketing campaign funded by the product company. This one is being run as a specialist company and for less than a fiver (GBP) could be worth the money. We’ll just have to wait and see.