Jailtime is needed for people that are a danger to the general public and need to serve time for offenses that have voilated others rights. Personal drug use does not violate others rights or saftey. Most drug users are also non-violent and dont need to be seperated from the public. However drug users that are a problem such as those who steal etc. to support their habit DO need to be given jail time.
A college student that gets caught with a little weed or blow doesnt need to be put in jail because that is simply a waste of money and resources.
As if our high schools and universities weren't graduating enough idiots, you'd legalize the possession and use of 'recreational' drugs so that we could graduate an entire generation of idiots that are stoned out of their minds to boot.
Then, in a few years, after half of these stoners have opted out of the work force in order to spend more time getting high, or, have been forced out of the work force through drug screening test (or would you abolish these also using a violation of privacy argument) we'll be spending the same about of money, or more, on the social programs than if we'd have locked up a few of the little snots to begin with.