It can happen, if the fielders get complacent after a run-down:
When Braun and Segura both wound up at second base, Segura, as the leading runner, had the right to the bag, so Braun was out when he was tagged by Cubs third baseman Luis Valbuena even though he was standing on the base. However, Valbuenna, though he tagged Segura twice, never tagged him off the base (if you pause the video on the second tag you can clearly see Segura’s left toe on the base), so Segura was able to retreat safely to first base, though he needn’t have done so. He was safe on second.
SI has the video.
The Cubs still lost, because as bad as their fielding was, their hitting was worse. Oh, and manager Dale Sveum got thrown out of the game, too. Awesome.