No, it's not safe, you run the risk of dangerous levels of awesomeness.
J/K, It's safe as far as I know. A few people have asked me about "potassium overdose", but you would have to eat like 400 bananas in 30 seconds to get to a lethal amount of potassium. One important thing is to always eat ripe fruit. So for bananas they should have brown spots on them. Then they will be an excellent source of soluble fiber, they are digested quickly and burned as energy and they satisfy the sweet tooth.
One thing that I personally think is important is that for all the sweet fruits I eat I try to eat a comparably larger amount of greens (spinach, Kale, Chard, lettuce, dandelion roots) I eat about 1.5 pounds of greens everyday.