I'm not a lawyer either, but my reading of clause 3.2 is similar to
Jan's. Thingiverse can't do "whatever they want" with what you post
there. That clause says that the rights you give up to thingiverse are:

"solely for the purposes of including your User Content in the Site and
Services."

Services being defined as:

"service for users to share digital designs that can be printed on 3D
printers to create physical objects (collectively, with all other
services provided through the Site, the "Services"".)

The uses that license covers them for include things like storing copies
on their servers (reproduce), generate rendered previews of 3d model
files (ie derivative works), featuring designs on their site front page
(ie publicly display and perform), and the other things that they need
to do to run the site.

The license they ask for is neither transferable to other parties nor
sublicensable (unlike Facebook, among many other sites.) So it only
ever applies to them.

The worst thing I can see about the license is that it's
"irrevocable", so even if you cancel your account Thingiverse LLC still
has the right to host your content on the site.

It could no doubt be better from our point of view, but
in my opinion comparing it to the expandable/catch-all copyright
licenses used by some other sites is totally unfair. Thingiverse also
has to protect themselves from frivolous lawsuits.

With some luck the smart minds at http://tos-dr.info/ (a great site!)
will come up with a nice summary soon.

Anyhow, that's my uninformed 2c (sorry for such a un-hackery first post
to this list!),

- Angus