Could someone who eats too much fruit be just as much at risk for diabetes as someone who gets sugar from other sources? (perhaps overweight as well.)

Unlikely: Diets rich in the anti-oxidant vitamins a, c, e, and selenium are considered protective. Fruits and vegetables, in variety, and not eaten to excess, is advisable. That said, consuming so much fruit that obesity is the result is ill advised. Everything in moderation, as we say!

No one has ever: Gotten diabetes from eating sugar. It's total calories and obesity that contribute 70-90% of the risk for developing diabetes. If you're overweight get educated and start losing weight through a restricted diet and increased activity before it's too late.