Here'a couple for starters. 1. They don't work well in multiple browser tabs. Specifically if you're storing a lot of data in memory it gets duplicated between

Here'a couple for starters. 1. They don't work well in multiple browser tabs. Specifically if you're storing a lot of data in memory it gets duplicated between tabs. Perhaps shared workers might be a solution in the future, but not now. 2. They allow designers to "enhance" the UI in new and wonderful ways, which isn't always good for user experience. It's like being tele-ported back to the windows native apps days. Plain old web apps forced simplicity and consistency in how things worked across the web. With spa's not so much. 3. Harder to test/re-create error conditions because often state of an application isn't represented in the url. (though it can, with good app state storage/structure, actually be better I think) 4. Harder to deploy new versions to apps sitting in users browser. So a user loads your wonderful spa app and leaves it open all day in their browser. You deploy an updated version mid day... how exactly does that user know to load the new version? In traditional web apps, updated versions are loaded on next page load. 5. You have to do something for page loading indication, since the browser no longer gives any indication it's waiting on the server for new data.