Coming from a law background this makes me, and I imagine many lawyers, nervous. Terms of Service agreements may be wordy and hard to understand, but they're also substantive--everything in them has meaning. Good lawyers should craft them to be as concise (and readable to lay people) as humanely possible, and there's no reason to believe that the lawyers that draft ToS agreements, particularly for highly profitable businesses, have done anything but that.

Even if you have a normal ToS and then try to abbreviate it, you have a host of issues: which one would control? You could explicitly say, "the normal ToS controls in the case of a conflict between the ToS and an abbreviated version," but, if people, don't read the normal ToS because there is an abbreviated version, is it really conscionable to say that the normal ToS would control? If the abbreviated controls, there have to be many caveats: like "We own everything you upload... unless you didn't own it to begin with, in which case, we don't own it, and you guarantee to us that you have the right to use it, and you give us the right to use it," or "There are no warranties, except if this statement itself is unenforceable (which is true in some states), in which case we disclaim all warranties to the extent applicable by law, and in the event this is unconscionable or found unenforceable, the rest of this agreement is still enforceable" etc etc. Once you're in that land, you've obviously lost the point of abbreviating it.