If you really need evidence, I think a great example is subsidizing single motherhood. In the US, back in the late 1950s a debate started about whether or not to extend needy family benefits to unwed mothers. Edit: from Megan McArdle (thanks Vladimir M.):
But if you give unmarried mothers money, said the critics, you will get more unmarried mothers. -Ridiculous, said the proponents of the change. Being an unmarried mother is a brutal, thankless task. What kind of idiot would have a baby out of wedlock just because the state was willing to give her paltry welfare benefits? -People do all sorts of idiotic things, said the critics. If you pay for something, you usually get more of it. -C’mon said the activists. That’s just silly. I just can’t imagine anyone deciding to get pregnant out of wedlock simply because there are welfare benefits available.
By the early 1960's the black illegitimacy rate in the United States reached an unheard of 25%. By 1990, that rate was 70%. All this in spite of the development of the birth control pill, legalized abortion, improved contraception, etc.
And of course this had nothing to do with the war on drugs and the high incarceration rate of black males.
"Wet houses"-- subsidized housing for alcoholics (they need to get most of their own money for alcohol, but their other expenses are covered) might actually be a good idea. It's cheaper than trying to get them to stop drinking, arguably kinder than trying to get people to take on a very hard task that they aren't interested in, and leads to less collateral damage than having alcoholics couch-surfing or living on the street.
Utilitarians, what do you think?