if you feel inclined to get down and investigate for yourself and are capable, properly jack the rear end up ( be sure to chock your front wheels) so that a tire is off the ground. Hold the tire from the left and right sides and try to give it a wiggle and then do the same while grasping it from top and bottom. Repeat with the tire on the other side.
Check all your lug nuts too. Sounds silly but I've had scary shaking be nothing more than lug nuts not being tightened down.
A worn shock will cause a boat-like driving behavior. However, a **blown** shock will cease to dampen all impacts and will instead cause a pogo-like effect. It is dangerous to drive with a blown shock. Ever bounced a tire on the ground? Essentially, your wheel will be bouncing up and down like crazy.
I have an appointment on Thursday to have the struts and mounts replaced with Monroe Sensa Trac 171798 Quick Strut Assembly and a 4 wheel alignment. Then like I said I'm gonnna take it from there. I'm prolly just gonna replace the rest of the rubber stuff (sway bar links, bushings, ball joints, etc.) when I get paid again. RockAuto has that stuff pretty cheap. After that I don't think there is anything else that can be replaced!
got the pa back today. rides like new. gotta love pep boys 2 new monroe quick struts, alignment, installation, and extended labor warranty, all for $300. Cant beat that (unless you do the work yourself)