Virgin Blue Toilet Seats

I have been flying a lot lately. Mostly from Perth here in Western Australia to Sydney and then on to other ports. In the last 3 months or so these have included Brisbane, the Gold Coast, Sydney, the Sunshine Coast and even Osaka in Japan.

I have experienced a number of airlines in these sojourns including Qantas, JAL, JetStar and Virgin Blue. And there are a number of aircraft types in this mix too - 747, 767, 737, Airbus; and I have noticed something very, very odd.

Only Virgin, whose service by the way is very good (but Qantas is preferable ex-Perth to Sydney as they deploy 747s) and they have a record of being the least tardy on take off times, has toilets seats that will not stay up in flight!

Is this deliberate? If anyone can tell me ...