Giving a child of 2 the option of saying I will sit on mummy's lap or I don't want to do that when a bus is full is not acceptable to my mind. HOWEVER, the idea that because a child doesn't pay s/he is not entitled to the safety of a seat is absolute rubbish and it's no wonder that some young people think us oldies are anti-child. The key issue here is safety - children cannot anticipate in the way that adults can - a bus lurches and an adult can respond whereas a child can be totally shocked and fall. Living in London I use buses and tubes regularly, and whilst I would always put my grandchildren when they were babies and toddlers on my lap, I would never ask them aged 4+ to stand for an older person because it's far more dangerous for a child to stand than it is for an older person. And let's be clear about who pays and who doesn't - ultimately all services whether private bus companies or trains - use the infrastructure that is paid for by taxes which we all pay, including the parents of those kids. The other thing to remember is that there are many reasons why a child may not be able to sit on it's mother's lap but which you as a fellow traveller can't immediately see, i.e., the mum may be pregnant or not feeling well. More tolerance from everyone is required in this whole matter.