In January 2009, the Finnish government decided that all Finnish passports will incorporate fingerprint information. Over several protests from officials and citizen groups, the fingerprints were assembled into a database. We were told at the time that the database wouldn't be used for anything except identifying dead people.
Here's the question: how long do you think it will take for the Finnish police to get unrestricted access to the fingerprint register?
Yesterday, the minister of the interior announced that the ministry is looking into allowing the police access to the register "to solve serious drug and sex crimes". Now, I'd argue that under Finnish law, there is no such thing as a serious sex crime (see here), but nonetheless, this is what they're doing (sez Hesari).
If all goes as usual, the next parliament will probably approve this. After all, they'll use it to catch paedophiles. You don't hate children, do you? After that, how long until the definition of "serious crime" gets expanded? And, after all, the Finnish police will never exceed their authority.
Funny but true: according to Finnish Wikipedia, the slippery slope argument is a fallacy.