Reasons to worry about the US economy
The same US economic perma-bears have been saying the same things since 2009 but that doesn't you can dismiss them completely. They're very good at highlighting vulnerabilities.
Here are 58 facts about the US economy (all one one page). It's a good time of year to take all sides into account. I'd say about a dozen of them are definitely worth keeping an eye on, especially the long-term demographic/structural problems.
But remember that being right doesn't necessarily pay. The timing is everything and if/when then next recession hits, there are no prizes for being extra early.