The only explanation I can think of for this obviously irritating behavior is demand elasticity at work. My guess is that fewer and fewer people make calls using their room phone, instead using a mobile phone. So, Starwood probably figures that the people who still need to use the room phone have a very urgent need to make a call and will be willing to pay up for it. This might be because their mobile is broken/has a dead battery, is out of range, etc. Then there are data calls -- people on the road need to check their email and are willing to pay for it (exorbitantly, in Starwood's case).
Something very similar is happening to pay phones. In most places, pay phone calls cost 35 or 50 cents nowadays and there are fewer and fewer of them.
Good news is that this will all be moot in 1.5-2 years when broadband wireless becomes a reality. Of course, then Starwood will probably install jammers at its hotels and charge $20/day to deactivate them.
[This message has been edited by smg77 (edited 08-06-2001).]