The site http://touchstack.com/tex.stackexchange/questions seems to be reposting all our questions and answers (and http://touchstack.com seems to do it for the other Stack Exchange sites, too). I do not like this, but the real question is: Is that legal? (If it isn't: What can be done about it?)
Yes, I'm very much in the wrong here. Touchstack was originally intended to be a smartphone web client for Stack Exchange sites (using the API), but I ended up rushing it out so I could show it to a few people. I posted it on Stack Apps as a work in progress, intending to update it over the next few days and bring in a lot of features that were missing. It so happened attribution was one of the key things that was missing.
As per life, I ended up moving onto other projects (amongst schoolwork, university application etc, arguably much more important) and completely forgot about Touchstack. Then SE mobile shipped, and any impetus I had for working on anything to do with Touchstack was long gone. Attribution was somewhere in a long list of forgotten updates for the project.
Needless to say, since an official version of mobile SE was released there is little-to-no point of Touchstack - it's just wasting Heroku's resources. I was going to leave it to rot once the domain expired in May, and so instead of updating it now, I'd rather just kill it off.
So yes, I'm sorry for misusing your content without correct attribution. The issue will go away shortly.
Also do check out Stack Apps if you get some time, it's full of other cool things.
It looks pretty much legal to me, have a look at who's behind TouchStack. At least, it has been created through the SX web app system, and it looks ok with the moderators. One should also note that it does not seem to be importing the actual questions – more like, it seems to access them through Stack Exchange.
Regarding what is legal or not, all contributions to this site are subject to a Creative Commons Licence, which clearly states that anyone can copy and redistribute the work as long as they provide attribution.
So, it does not seem to me that they are doing anything wrong from a legal point of view, although one could argue that they should make it plainer that it all comes from Stack Exchange sites (by providing back links and an info page, for instance)… but then again, it looks like that app is still very much in beta. You could ask the developer to provide such information, though.
All posts on all stackexchange sites are under the CC license, originally v2.something, now v3.0. This license allows to share and adapt the content freely. You accepting this license when posting things here. I don't think the stackexchange people have anything against this. They actually provide an API to access all posts and touchstack seems to use it.
Looking at https://stackapps.com/questions/2478/touch-stack-smartphone-optimised-stack-exchange this sites seems to target smartphones and simply provide all posts in an format optimised for them. So this is apparently a feature not a bug, aeh break of copyright.