Useless?
These immigrants are the folks that have laid the base Germany's economy over the last forty years. Without them, Germany wouldn't have had enough warm bodies to fuel their growing economy.
Despite that the fact that these folks were essential for the economic growth experienced by Germany, the country has turned their back on them now that things have slowed down. I'm sorry, but that isn't right. You depend on these people and they give up their lives, families, and everything else to move into your country and then, suddenly, you sweep the rug out from under them?
Guess what happens when the economy picks back up? Germany will open its doors again and tell these people how happy they are to have them. They'll be begging for them to come back.
It's disgusting and it's disgusting the way that they are treated within the country.
And, even if you do think it's right, it has lead to tremendous problems within the country, most of which could have been avoided if these people had been offered a path to citizenship and if the country had made an effort to make them Germans.
Germany and France are both guilty of using these people and now they're surprised that:
(a) after ten, twenty, or even thirty years within the country these people don't want to suddenly pack up and move? Many of the "turkish" people that live within Germany have never been to Turkey. They've lived their entire lives in Germany. They are only not "Germans" because Germany wanted it that way... and now they don't.
b) that their country is suddenly less German? It is foolish beyond belief.
These immigration issues are a classic case of wanting to have a your cake and eat it too.
That's not really the issue. Foreigners who have been living in Germany for 8 years (this can be reduced to 7 by attending an "integration course" which is mainly a crash course on language, laws & culture) can naturalize there, see: http://en.wikipedia.org/wiki/German_nationality_law
Now, a little perspective on the issue:
Originally, in the sixties, Germany hired workers from abroad because there was a lack of workers. The idea was similar to the American green card system: you go there to work for a few years and then go back. Germany didn't want to become an immigration country at that time. The idea of becoming an immigration country was generally not exactly widespread in Europe at that time. These people initially came without their families, because they planned to go back. Usually, they didn't try to learn German beyond what was necessary for work (which often wasn't much, they were usually hired for rather simple jobs).
Then, after five or ten years, when it became clear that they would stay longer than initially planned, their wives and children moved to Germany. The children were often already 5, 10 or 15 years old, so a good part of the 2nd generation had grown up partly outside of Germany as well. Later, in the case immigrants from Turkey, when this 2nd generation married, they often married wives or husbands from Turkey who then moved to Germany but again were 1st generation immigrants. Also, there has been ghettoization in places like Berlin-Kreuzberg.
The children of these immigrants still have much worse average results at school. This isn't much of a surprise when many don't talk German at home or with their friends. Also, in some cases the cultural background makes things even more difficult (eg. boys with a muslim background often don't respect women as teachers). As a result, unemployment is siginficantly higher among this group.
Now, there's welfare that's being paid to jobless people in Germany. For example, a family of five can get around 2100-2500 (depends on things like rent and heating costs) plus health care. At the same time, the low salary sector has grown in the last two decades, so there are quite a few people who work and barely make more money than a family that's on welfare. So that's an angle that's easy to exploit for pupulists and demagogues.
A few months ago, a former politician who had moved to the German central bank (Thilo Sarrazin) wrote a controversial book in which he described some of the existing problems, but then drew some rather crazy conclusions and basically said that Turks and Muslims are unwilling to integrate themselves and culturally backwards and that if we needed immigration, we should rather let hard working Asians in instead of lazy Turks, Arabs or other Muslims who will only collect welfare. That led to rather heated debates, Sarrazin had to leave his job at the central bank and lately a right wing politician (Seehofer) said that "it's obvious that people form other culture groups [ie muslim instead of christian] have mor difficulties integrating themselves into our society so it's obvious that we don't need more immigration from other culture groups". Which lead to another heated debate.