Are running injuries directly related to body weight?

I had read somewhere where for every pound of body weight translates to like 6-10lbs extra force on your joints -  hips, knees, ankles.

this isn't the exact article, but close..http://dougfioranelli.com/seminar-review/ucsf-sports-and-injury-rehabilitation-conference-recap-running-injuries-5/

I'd say it greatly depends.  Male vs Female will make a huge difference with certain types of injuries.  More weight will increase overall ground reaction forces, but then there's how you run and how that changes the impact force (your gait biomechanics).  Bigger people tend to have bigger ligaments/muscles which, all things being equal, should have a higher tensile strength, although this scaling effect isn't linear, then there's other properties of the tissues that come into play (elasticity/stiffness etc) which vary from person to person for a variety of factors including some I mentioned above. 

I, personally, think injury risk is more closely related with mileage and overuse, and all of the factors I mentioned above modify your risk.

Weight is not the only contributor, but it certainly increases the risks.

Same joints +higher impact forces = higher injury risk.

As already stated: it's one factor, but not the only one.

When I weighed 135ish pounds on my 5'8" frame, I experienced 5 stress fractures just about simultaneously. I think it was mostly because I'd not run much ever in my life so my body wasn't ready for it, but 90% of the other folks in the same situation didn't experience the same injury, so there has to be more to it.

Well I would bet it's form and over use.  I am heavy, especially on a 5'3" frame. (not going to put my weight) My husband and I started running in October 2010.  Although we were somewhat active prior (long time road cyclists), we had never been runners.  We are in our 50's so we took it easy and did NOT run every day and practiced smart increase in mileage week to week.   I did four 1/2 marathons last year and one this year.  I have never had an injury.

My husband who just qualifies for Clydesdale and is only like 5'9" and was injured in September last year, been in PT and has only started running again.   It's still hard for him, he feels it in his calves and bottoms of his feet.  In physical therapy they figured out from an old snow boarding injury where he broke his heel, he was overcompensating and not running correctly.  Most of his recovery was working on strengthing core and hips.

I still don't like to run and don't consider myself a runner, but it certainly is good cross training for riding and swimming.

When I was heavier, I never had injuries. I always kinda HURT when I ran, but I was never injured. Since dropping 35 lbs I've had a stress reaction and a few different varieties of muscle strain and tendonitis. However, I didn't try to run marathons when I was heavier either!

I think my flat feet and my stubborn streak have much more to do with my injury prone-ness than anything else. I am bummed, though. I consider myself to be more injury prone than others I know. Following the same training plans, I seem to be more likely to be injured. Since last year, I changed my shoes and changed my running form and felt much better - and got the same injury that plagued me last year.

I'm 5'5" and 135 lbs (carried mostly in the butt/thighs).

I don't think it is the only factor.  I ran a marathon at my heavier weight, have since lost about 20 more pounds, and have had to change up my technique to avoid injury.  I have heard somewhere that for every extra pound of non productive body fat decreases your running performance by 1%.  

I think other factors would be strength and stabilization.  Some runners may carry extra weight, but their joints are able to compensate for the higher impact.  I would always suggest strength and flex training no matter your weight.  I also think you need to look at your strike and adapt your shoes.  It is possible to have a different stride with a little more weight on.