Work experience is important and makes you more marketable for better jobs. Even if it's mundane work, it's still experience.
As someone who started working at 16 (I started working in retail at a True Value), I think job experience is crucial and you should seek employment as soon as you are able to work. As far as I'm concerned, even if you graduate college with a 4.0 majoring in engineering, physics, or pre-med, it'll be debased significantly if you have no work experience when applying for an important job. Even an internship will go a long way. I currently work as a paid student aide for the Army Corps of Engineers. Most of my work is boring, but I'm getting used to the federal environment. I've also had some experience working in a laboratory at a previous summer job.
Personally, I set the bar at 21 (keep in mind, this is me being generous). If you're 21, you have no job, and/or you aren't in some kind of school, you aren't doing anything useful for your parents/roomates, and you're perfectly able to work, you're a parasite; get off your deadbeat ass and go do something.
I think working during college should be mandatory at a certain point. If you're in your third year and you aren't paying at least a partial amount of your fees out of your own pocket, start working. Stop relying so much on your parents and loans; paying for at least some of your own education is a good lesson in self-reliance. If you can't get a paying job, at least find an internship and get some amount of experience.
Also, I think stating that "I can't because of the economy" is a lazy cop-out excuse unless you actually put a considerable amount of effort into trying to find an occupation.