I've never had any formal training or lessons of any kind...
Now I'm a little hesitant to say that, because I consider my own tenacious appetite for learning more about the things I love to do to be enough training in itself.
I've taught myself many different kayaking strokes, from functional, basic strokes to fancy, superfluous instructor strokes. I taught myself how to roll, and I am confident doing so in the white caps of the mighty Lake Michigan. I have practiced wet exits in full insulating layers, a drysuit, and my PFD. I've taught myself several different self rescues and am comfortable performing them in adverse conditions.
I didn't go out in 19 degree weather my first time kayaking. I didn't experience the chop of Lake Michigan until after the first few months. You have to kayak within what your abilities allow. It's when you over extend yourself that you are taking on too much risk.
Kayaking is an incredible way to experience the world. It's not difficult to learn, but someone can easily find themselves to be "in over their head" if they go exploring rock gardens during surf or going on whitewater before they are ready. The power of water is amazing. You really need to know how the boat responds in a variety of conditions before you will feel comfortable taking it out anywhere, any time, any conditions.
Let me know if you have any other questions!
JGON