A tad of paranoia don't you think?
It does happen - often just one parent travelling with a young child. I see it all the time - frequently young mum's travelling with one or two of their offspring and that does mean a stranger frequently being seated one side of the child.
What's the problem? Everyone is a molester until proven innocent?
No, I wasnt implying that. It's not paranoid to want to be able to buckle up / help with meals / get to sleep your 3 year old. Not being sat next to them makes it more difficult and awkward for both the child (as they are sat next to a stranger) and the person they get sat next to. The word 'stranger' doesnt imply molester.