I'll be 26 in May and I'm staying with my dad while I finish this last year of graduate school for my Masters of Science (last year meaning I should finish in December). Most of my undergrad time I stayed at home too since school was like 20 minutes away. I lived away from home my first year in college when I was at an out-of-state school and last year I lived on my own in an apt. in the town my grad school university is in (and I occasionaly live down in Hampton, VA when I intern down there). The year I lived at my grad school I actually ended up making 23k that year between my internship, my university stipend, and another part-time job, but living expenses in the college town are crazy (relative to Central Virginia) so not alot of that 23k stuck around very long.
Frankly, if you can live at home when you're in school I think it's great, because it helps save money, but it's important to realize that the only expenses I don't pay when I'm at my dad's place are my living expenses (rent, some food though I mainly buy my own food, utilities, that kind of thing). Everything else I pay myself - car payments, health insurance, car insurance, phone bills, credit card bills, miscellaneous expenses, etc. - I NEVER hit anyone up for cash - NEVER.
Of course, the appropriateness of this also has to do with your relationship with your parents. My relationship with them is fine, everyone except the older parts of my extended family know I'm gay, and my social life is fine, I come and go as I please whenever I please because they're not over-protective or anal and I don't take undue advantage of the good situation I'm in (nor do I take it for granted, I've been lucky in basically having a free-ride financial-wise in my entire education).