Fairdealfrank I too am familiar with the revenue protection approach by LoCos, and I can actually understand (but not necessarily agree to) their desire to prevent cheap bookings being sold on or given away. Hence their enthusiasm to correlate ID with the boarding pass. BA and good old BD don't do this.
I also recognise the need to present a passport when travelling out of the UK; airlines understandably do not want to pick up the cost of repatriating those not eligible to enter the destination country, or incur fines and so on for transporting said undesirables.
Flightrider I too resent the requirement to produce a passport or similar for an internal flight (subject to the revenue protection argument). BA's only stipulation is that you bring the credit card you used to pay for the booking with you. I'd like to get to the bottom of this one though as a while ago the was some political shenanigans betwixt the UK, IoM, CI and Eire about having to pass through passport control when entering the UK from said countries, and thus the abandonment of the Common Travel Area. The then IoM Chief Minister negotiated and eventually assured us Manxies that we would not need to show our passports to enter the UK. So either the IoM Airport people, the IoM cops, Special Branch or IOM Immigration are now insisting on the opposite, or, I suspect, the handling agents are programmed to apply the same ID requirement regardless of airline. If the former I'm going to raise it with the politicos. If the later I'm hoping that someone from Menzies will confirm it's a SNAFU and sort it without any embarrassment to their staff.