Britexpat, as usual you have hit the nail on the head. I do feel for those guys but I don't believe they are being exploited unless they were promised something different and then made to do this. I take the bus from Dukhan to Doha several times a week and the road workers use the bus to get from one place to another. They have a real laugh and sometimes even let me in to the joke. It is sad that other countries are still corrupt, dangerous places to the extent that it is preferable to spend 5 years here, away from family, working in the heat. I do not think that Qatar is any worse than many other countries, let's face it, without illegal immigrants the UK hospitality industry would be finished. The law in the summer months banning outside work from 11am to 3pm, at least on the Dukhan road has been largely observed for the last 2 years.
By the way, I love living in Qatar but do feel self conscious about the status us Westerners have sometimes, for example the other day when renewing the car insurance the man called me to the front of a very long queue. I am not sure what us Brits have done to deserve such reverence.