the TS in PTSD stands for "Traumatic Stress"
Since everyone handles stress differently, I'd imagine the bar for what counts as traumatic stress varies extremely from person to person. Some people here have proven that they get serious emotional investment in internet relationships and online social engagements and that could probably result in some heavy stress. Coupled with the ever-looming idea of private investigating and ddos attacks over mild sleights, the concept of getting PTSD from the internet doesn't seem too far-fetched.