Spending lots of money for little/no result! From Geek with a .45 we find a link from the Maryland State Police that basically admits what a waste of time, money and energy their program has been, and asking they be allowed to basically dump it; there are places the money & people can be much better used.
Of note in the document is their admission that of the very few 'hits' the got, NONE were used in prosecutions. So for years of annoying the citazens and putting one more roadblock in the way of honest gun folks, and spending millions of tax dollars, benefits have been zero. Unless, of course, you're one of the people who thinks that making it harder/more expensive for people to own guns makes it all worth it.
Instapundit has had a number of posts on this kind of mess, in particular ref a study in California (here and here are two). Among other things I thought were interesting was that not only were perfect matches fairly rare when using the same gun and ammo for tests, but simply changing the brand of ammo took another big bite out of the accuracy.
It seems that the enthusiasm for these programs come from two things: one is a misunderstanding of how accurate they actually are, and second is the desire of some to make ownership of arms as expensive and difficult as possible.
Side point: last I heard, Canada's national gun licensing scheme was now somewhere between 500 million and one billion dollars cost. I forget how many hundreds of times over the 'official' estimates this is.