Personally, I like mixing the running and exercising but there are days, usually when I'm hurting pretty good for whatever reason, when I will only exercise or where I will only run. Then there are lighter/heavier days, faster/slower days, days where I'm doing something unconventional, etc. Someone passing by or just coming in might see me all sweaty and dying with only a pair of 2-3 lb dumbbells in my hands and think man that guy is weak!
Usually, I'm just happy to see people working out at all. If I KNOW for sure that their workouts are "less well rounded" (e.g. running only or lifting only), I will try to encourage them to change it up or add this or that. I also like to show them how to apply their attributes towards DT/MA/MMA but it can be like pulling teeth...
"If You Open It, You Get The WHOLE Can." - Capt. "Petey"
Igitur Qui Desiderat Pacem, Praeparet Bellum - Publius Flavius Vegetius Renatus
"Absorb What Is Useful." - Sigung Bruce
"Stupidity isn't supposed to make sense. That's why we call it stupidity." - Big Sexy
"**** 'em, just shoot the **********." - Cat Doc
"You can't let a fat chick make you sad." - CityOfChicago
"Somebody needs to start issuing lives to people." - RDS