Corporate users of 3G dongles used to rack up enormous charges while roaming. They’d get hit with five-figure bills and complain to their carrier that they didn’t warn them, and often the carrier would end up swallowing the charge, even though they were rarely marking up the costs heavily. I worked on a project with a major carrier to enable companies to monitor and alert on cost overruns, and shut off devices in some cases. But before we launched, the EU basically cracked down on the underlying charges and made roaming far less stressful for everybody. Shame, because we had quite a nice end to end setup that would test real world usage on many combinations of laptops and dongles and ensure everything triggered properly.