You could sue them if they don't deliver anything at all, Kickstarter explicitly leaves that door open, not sure if anyone ever tried.
Agreed, and there have been some attempts. The biggest problem is that, as a backer, you have no visibility into who the other backers are, or what they may or may not have received. So, it is incredibly difficult to form yourself into a "class" and take them to court. Plus, in most cases where projects collapse, by the time you get everything assembled to sue, there is no entity (or bank account) left to sue. The article on Ars I linked above goes into a bunch of the issues on that end.
I'm not suggesting Kickstarter is "bad" at all. But, to answer this question:
I mean, do the people that pledged have a share of the company after than and are entitled to a share of any profits moving forward?
It does
not. Just ask the people who backed Oculus. Backers
should be entitled to some kind of product (as Nathan indicated, like a pre-purchase), but
there is no guarantee, and it is very difficult to enforce this if the devs disappear or their company collapses. This can, and does happen.