Pay-as-you-go-Internet access

I noticed this in Penang and in Bangkok. You pay about USD150 for a modem and for 3GB and then you have the option to top up. This may be attractive if I were more familiar with the carrier's coverage and did not have access to hotel internet (or if the hotel internet was expensive as it was at Katathani). I also started noticing them in Washington when I got back but instead of a fixed bandwidth amount Verizon and ATT charges by 12 hours, week or month which is not very useful. In fact, it's downright useless.