Ok this has happened to me twice... I did a little looking around and some of my own investigation and come to the conclusion that there are a few factors involved that cause this problem:

1) the bolt hole that holds the bolt may not be deep enough and bolt stops early and the shims/bushings aren't thick enough to make up the difference.

2) the bolt could possibly be backing out and the stress snaps the bolt at the thread line?

3) the bolt is a flimsy piece of shit and the designer at the HD Factory should be bitch slapped!!! 

in the picture are two of these bolts, one of them is a bolt that sheered in June of 2010 the other a brand new HD replacement sheered today! April 23 2011:P

Yeah I'm not skinny but THIS should NEVER happen and it snapped on me when I was out riding and the wife was a passenger, and she's skinny!

I think option #3 is the best !!!!!!

Does not sound good at all.

Looks to me like they were not tight enough, but it could be that you have a bad shock and it is stressing the bolt too much for a single shear application.

You're probably correct on #3 of your list. If it were mine, I would go with Mike's idea on the grade 8 bolts.

UPDATE: I sent a letter, somewhat like the posting I left here to Harley Davidson and today, at 1000 hours this morning I got a call from Wisconsin!?!?! Guess who? Matt Gartman of Harley Davidson that's who! Anywho, he wanted me to elaborate further on my problem and then he advised that they have an update which is the frame mounted design with the stud into the frame and so forth(y'know, how they're suppose to be made?).
Anyway he says I'm going to call your closest dealer and we're going to take care of this for you at no charge... I sat on the phone waiting for the other shoe to drop. So after being on hold for about 10 minutes Mr. Gartman's back on the phone to me explaining that he talked to George in the service dept of Monterey County HD there in Salinas CA. At the end of the conversation Mr. Gartman gave me his direct line to call if there were any further problems on my end and thanked me for my letter and time and I thanked him for throwing me a bone on this shock mount issue!

No sooner than I hung up George from Monterey County HD called and let me know that they should have the part in soon and he would call and make arrangements with me when it came in, the ONLY part I'm respnosible for is paying for the shipping for said part $15.00. I thought, hey, that's a small price to pay to get that problem fixed, George informed me that I was lucky because it's rated as a $200.00 fix. So any of you 2006-2007 Dyna owners beware, these first year designs are so much fun to flush the bugs out of!
I have a lot of miles on my 2007 Dyna and I know that I have exposed a pretty good weakness so I hope this helps whoever might have this issue down the road or prevent said issue. The upgrade was applied to the 08's and above so you guys are set.

Thanks, me too... now they're just waiting for Harley to send the dealership the special tool that installs the studs.

I have asked that question to my buddy who is an electrical engineer and he said its easy, if I don't keep designing and engineering things I don't have a reason to demand pay at the end of the week, just like anyone else who works for money. So I say to him why don't you leave stuff alone that works great and he said thats what an engineer is. Its easier to tinker with existing items than to go out on a limb and design brand new products.  but I agree with you Mike 100%, if its not broke then don't fix it!  

Yeah and this design was on the side of ridiculous, my 94 Wide Glide NEVER had this sort of problem because of the stud in the frame design. So instead of designing NEW things these engineers play with the old stuff and assume they're making it better or more cost effective? Sometimes I think the cost effective point is what the actual angle would be since HD is always trying to find ways to save money.

Can you satisfy the idle curiosity of an old man & have somebody run a Rodkwell test on said, failed bolt.

Picure looks like something from Tractor Supply, & not the good Grade 5 or 8 bins

Harley says their Grade 8 and I laughed at Matt when he told me this. I will find someone to test them when they pull the other bolts.