Of course it is. That's no reason to ban it, control it or worry too much about it. Bruce Schneier tells everyone to take a deep breath:
Criminals have used telephones and mobile phones since they were invented. Drug smugglers use airplanes and boats, radios and satellite phones. Bank robbers have long used cars and motorcycles as getaway vehicles, and horses before then. I haven't seen it talked about yet, but the Mumbai terrorists used boats as well. They also wore boots. They ate lunch at restaurants, drank bottled water, and breathed the air. Society survives all of this because the good uses of infrastructure far outweigh the bad uses, even though the good uses are - by and large - small and pedestrian and the bad uses are rare and spectacular. And while terrorism turns society's very infrastructure against itself, we only harm ourselves by dismantling that infrastructure in response - just as we would if we banned cars because bank robbers used them too.