It's important to understand the distinction between a DNA sample and a DNA profile. In nearly all coverage of the UK DNA Database, the two terms are conflated or used interchangeably.
A DNA sample contains genetic material which contains 3 billion base pairs. That's about 750MB of information.
A DNA profile is a something like a hash code of this information containing 20 points. I don't know the exact data size - but I'd be surprised if it was more that a few kilobytes.
The procedure in UK has been to take a DNA sample, create a profile of it, and then keep both. The profile is stored in a database, and the sample in some kind of laboratory warehouse.
Whether you agree with it or not, there is an argument for keeping all DNA profiles on a database - the database can identify individuals. It's used currently to identify murderers from crime scene DNA, and within about 10 years it'll probably be used to identify householders who haven't sorted their waste into the correct recycling bins ;). That feature creep is inevitable, but it is largely predictable.
The argument for keeping DNA samples is 'We might think of something to do with them in the future.' - That's 750MB of data on each individual. Future developments in DNA analysis mean that data could be used in ways we can't even imagine now. The scope for feature creep is enormous.
That's why it'll be a victory for civil liberties to see DNA samples destroyed six months after collection as proposed in the 2009 crime and security bill. It doesn't look like the goverment will fully comply with European law (deleting all DNA profiles of the innocent), but it is a big improvement on the current situation.
Link - Alan Johnson on the DNA Database (The Guardian commenters seem to have missed the good news about the u-turn on the destruction of the samples)
Dr. Mike's Education Blog today features a good list of free software tools for use in education. There are lots of lists and sites devoted to free software out there - but this one provides particular value because of the recommendation to use the software in a specific context - the classroom. Each tool has a description and website link.
I've updated the final figures for the October .NET Penetration statistics. Turned out to be pretty much the same as the reading taken in the middle of the month, suggesting no large gains for .NET towards the end of October.