IJ Reilly said:
That being said, I'd worry at least a little about any 17-year-old getting into a serious relationship. Very few people that age have the emotional maturity required to make it work.
The other issue I see is that people develop a lot between the ages of 16 and 21, many even longer, before they start to settle in to the person they will be for the rest of their life. A lot of changes are taking place during those ages, but to the body (iggidy giggidy

) and to the mind and personality of each individual.
I went to a HS that was a direct feeder to a local college. 80% + went to that college and they still seem to be in HS to myself and others who have gone out on our own, different colleges, etc. There is nothing wrong with doing what so many of those people did however it seems to me that they have not developed as their own person (in most cases) and their HS clicks are still very much intact. They develop as a group and not individually, which leads me to wonder what happens when college is over and they have to go function independently when all they have known for the last 8 years has been their group.
It's fine for any age to date, assuming both parties realize the social differences of mass gaps and are willing to deal with them. The issue I see comes with developing 'together' and not uniquely your own. Although some would say it makes your bond very strong, which it would tend to do, it can also shut off your bond to others. I'd say go for it, but have an open enough relationship that you are free to interact and grow with others just as much, or more, as you do with your significant friend/other. After all you only develop this stage of your life once, you'd hate to have that completely dependent on another being because as much as you believe it's forever now, things have a way of changing in the future. Go for it, just go with your eyes wide open.