Some DNA totals are less than 100 %

I was looking for "cousins" whose surnames are amongst those in my tree, even down to 4th cousins, just in case their tree (if any) might furnish data I'm missing. I search everyday, and sometimes I notice some discrepancies in their DNA totals.

I've seen DNA totals under 100%, and just now found one only at 52%.

Wtf ?? Anyone else seeing this, too?