I live in Denver and just resigned my lease without much in the way of increased negotiation power. I run into two main issues here:
1). Extreme information asymmetry. While many of the properties are owned by different investors, many of those same properties are managed by a significantly smaller subset. Those property managers have a cartel like effect. For instance, they can strategically hold back supply to keep a rent floor and 'establish' extremely draconian lease terms under the guise of 'market forces.'
2). Draconian lease terms. This is a subset of the 1st point, but it's extremely difficult to price the market when you're required to give (move-out) notice well in advance of the actual lease date. Because the market here is so fast, you're basically jumping in blind-folded at what might be available when you go to look for a new lease. Great for landlords you can fill a spot in a moments notice, but horrible for a tenet who's trying to understand the cost of such a decision.