As you might have heard at Opera we decided to support some vendor-prefixed properties from WebKit. For reasons unclear to me we explained this as a problem with developers and received criticism from e.g. Faruk and Wilfred. I do not think this is a problem with developers. Like everyone developers are constrained on time and will ship what makes them and their clients happy.
There are two problems here: slow standardization and impending software monoculture. Whether software monoculture on mobile is impending or has already happened we can tell in the future, but it is clear to everyone that WebKit is a dominating force. And the longer that continues to be the case, the more competitors will have to copy proprietary aspects, including bugs and misfeatures. Netscape 4 and Internet Explorer 5 & 6 have demonstrated that in the past.
Standardization in general is quicker these days, mostly thanks to the WHATWG which pioneered and changed many aspects of how standards are developed now. CSS however is still quite slow. End of 2007 Dave Hyatt announced CSS Animation on the WebKit blog. The first CSS Transitions Module Level 3 draft did not get published before March 2009. And now over three years after that first draft and over four and half since it was initially proposed, it’s still a draft with a theoretical ban on implementors to support it without prefixes. For a wildly popular feature proposed by the market leader on mobile keeping it prefixed for four and half years is just too long.
(See also Vendor Prefixes Are Hurting the Web by Henri.)