My girlfriend at the time got into this. I didn't run but expressed interest in giving it a go, so I got a pair of lightweight running shoes and she instructed me how to run "properly" like dogs and other animals, that is on the balls of my feet and not on my heels.
I injured myself on my first run and couldn't walk for two weeks. I still don't really know what happened. Nothing obvious happened on the run; I didn't fall or twist anything and wasn't in pain during or after the run. But when I awoke the next day I couldn't stand. I was very fit at the time due to daily cycling both as transport and as a sport/hobby. So my theory is my "cycling muscles" were way stronger than my "running muscles" and something in the latter just gave.
This theory was corroborated by the fact that I could not walk at all during my two week recovery period, but I could still cycle. I was in pain most of the time. It's the only time in my life I've taken painkillers regularly. It actually seemed to be getting worse, then one day I woke up, the pain was gone, and I could walk again.
Suffice to say I've never tried running in this completely unnatural way again. I've run since and never injured myself again. I run the way my body tells me I should run.
Forefoot running helped me tremendously, but the people in the shoe store advised me to use proper shoes for that (I guess I took the Nike Fly thing, which was good for that) and to start slowly with it. I used months to slowly adapt myself to it, starting with no more than 50 meters on these things per day, and I was already an experienced runner at that time.
I had a similar experience, except at the time I was an avid distance runner. I had run a number of ultras and was training for a marathon. After a single 15 minute run in a pair of Nike Free shoes, I was unable to run for two weeks. It felt like a combination of shin splints, knee problems, and calf cramps. It was horrible.
The strange thing was that I never really favored the big, bulky shoes anyway. I always sought out the lowest cushion, lowest drop shoes I could find. And in 2010 I was already 20 years into running regularly.
The fad did have a lasting effect on me though. I can now buy nice, low cushion zero drop shoes, and I love them. But no-cushion is definitely out for me, and I can’t imagine running shoeless at all.