The Kitchn tested four different ways to shape a burger to see which method produced a beautifully shaped, evenly grilled burger. These shaping methods are meant to avoid the sad bulging-in-the-middle effect that can happen if you don't do anything to the patty.
Bulging generally isn't an issue if you use a pan, but it can be a big problem on a grill or BBQ. The four methods were a regular patty without indentation, one with a shallow indentation like a thumbprint (as recommended by Bobby Flay), one with a deeper indentation (as demonstrated by Sunset), and one with "dimples" or little knife slits (per burger restaurant chain owner Richard Blais).
After grilling each burger, The Kitchn concluded that the shallow indentation provides the most uniform burger. We've seen this advice before, but it's interesting to see the method compared with a few others. For further edification, Serious Eats has a great piece explaining why the indentation works and how it helps you make a better burger. Visit the link below for more details on this burger experiment.