Muppet Alert......

[nigsy]

Do some phones not support tethering at the same cost per mb ?

Phone companies separate standard phone web access and tethering and usually charge much more for tethering.

I had no idea that was the case - that seems ridiculous for people (like me) who already have a data allowance. It seems absurd for people who don't go over the limit (even with tethering) to be charged - data is data at the end of the day isn't it?

You cannot detect tethering on a phone with a Google OS - Android phones, but Iphone users are being stung at the moment. Not sure how long the current state of affairs with Android phones will last though.