What would prevent my assets from reindexing on a local MAMP install
If the Update Asset Indexes fails on a MAMP install, double check to make sure ALL assets source paths are correct and exist on the file system.  

I had defined a asset source to a folder which I had planned on using but had not yet created on the file system, and this caused the Update Asset Indexes to fail w/o any warning messages, save for a JS error in the console.