... I run to prepare for real life. Not to be in the olympics. If i gotta run and leave a nikka i'ma be leaving him on concrete. Not a grass or asphalt. So i run on concrete, in nikes, around my neighborhood. Just like it would be if i was really running from a nikka. Proper preparation prevents problems.
+ i like running on the street more then a track or treadmill. You actually get to see people, get to know your city better, find all kinds of cuts. Better than staring at the same machine or track for an hour.
And i really don't think its that bad for your joints either.