I'm seeing what might be a trend of people using a chronological resume format but leaving off any indication of how long they held each position.
This is really not a good idea. It looks like you're trying to hide a series of short stays and in a pretty inept way, because it jumps out like it would if you left off any other important piece of information (like an email address, which I've also seen some people do).
As of today, I'm going to start emailing candidates who do this and asking them to submit a version of their resume that does include the time periods they held each position, since otherwise I'd need to spend time on the phone interview having them walk me through it for each job, which is tedious and not how I want to spend interview time. These shenanigans will not stand!