From the insurance perspective, "what are you thinking" often means, "you're driving a death trap... it's too small and will crush like a can." Not quite true, though... that's a topic for debate. I've seen crash test videos that convince me of above average safety. I've heard anecdotes of t-bone and rear-end collisions that cause > $5k damage to the other car and < $1k to the smart.
My first thoughts that motivated the purchase were of economy, unusual style ('coming out of my shell' - I'm tired of being boring), and the simple fact that I haven't used my Grand Am's back seat 5 times in 10 years. In this city, I can't accelerate fast enough to use the 140 HP in the Grand Am, even if I tried. Just end up hurrying to a stoplight... so, why waste the gas?
And for < $16k, I got safety and comfort features out the wazoo. My local dealers could only get me a 4 year old car with those features for the $15k range. A Prius with similar features was about twice as much.