The government has shown itself incapable of keeping our bank details secure. MI5 have left laptops in tapas bars.
Someone on this site got information from the sex offenders register from a relative
It's pretty clear that if this happened your DNA would become available.
Firstly there's the issue of reliability of DNA evidence. We hear loads of stuff about million to one odds and nobody ever seems to mention that it depends on how reliably the sample has been handled, the possibility of it being transferred from one place to another.
With a national DNA database you could be the suspect of a murder investigation because you were one of 20 people who happened to travel in a cab.
Then there's the issue of your DNA in the wrong hands. Maybe you have a nasty disease in your familly that doesn't affect you but do you want your employer to know, your insurer, your new girlfriend?
DNA blackmail could be with us very shortly.
Remember - you can change your bank account, you can't change your DNA