Dave Richards wrote an answer about Scarpa Spark Shoe - Men's on January 29, 2013
You've heard right, these do not have substantial support. They're a great, lightweight alternative to bulkier, more sturdy trail runners. What you give up in support, you gain in weigh savings. I personally have very narrow feet and am able to comfortably wear these without feeling like I'm moving significantly from side to side within the shoe.