personally you should give a middle name instead of one because for example if thomas smith gets arrested you can go oh thats not my son he is thomas mark smith or whatever...... also makes it less likely for confusion on any records to having someone else with your name etc.....
They usually go by dates of birth as well or another something else to identify someone because there's bound to be someone out there with the exact same name as someone else, including their middle name.
I'm one of three and my brother and I have a middle name but my sister (eldest) doesn't. Mum said she did this because her name is already long.
My DH and I have give our DD a middle name after my best friend. And when we have another we will give that child a middle name, just because we want to.
I don't understand the whole six middle name thing though lol