vs2011 std::async is buggy

#include <vector>
#include <iostream>
#include <future>
#include <thread>

#include <boost/timer.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>

struct Trace {
    Trace(const std::string& func, int id) : func_(func), id_(id) {
        std::cout << func_ << " begin, id: " << id_ << std::endl;
        timer_.restart();
    }
    ~Trace() {
        std::cout << func_ << " end,   id: " << id_ << ", dur: " << timer_.elapsed() << "s" << std::endl;
    }

    int id_;
    std::string func_;
    boost::timer    timer_;
};

int dummyExpensiveBlockingNetworkCall() {

    int id = boost::lexical_cast<int>(std::this_thread::get_id());

    Trace trace("net", id);

    int result = 0;

    boost::timer    tm;

    while(tm.elapsed() < 10.0) {
        ++result; //Busy sleep. Changing this to a "normal" sleep changes behaviour.
    }

    return result;
}

void slow() {
    int id = boost::lexical_cast<int>(std::this_thread::get_id());
    Trace trace("slow", id);

    std::vector<std::future<int>> futures;
    for (int i = 0; i < 10; ++i)
    {
        auto fut = std::async(std::launch::async, [=]()
        {
            return dummyExpensiveBlockingNetworkCall();
        });
        futures.push_back(std::move(fut));
    }

    std::vector<int> resVec;
    std::for_each(futures.begin(), futures.end(), [&](std::future<int> & fut)
    {
        resVec.push_back(fut.get());
    });

    /*
    std::for_each(resVec.begin(), resVec.end(), [](int result) {
        std::cout << result << ", ";
    });
    */

}

void fast() {
    int id = boost::lexical_cast<int>(std::this_thread::get_id());
    Trace trace("fast", id);

    std::vector<std::thread> threads;
    for (int i = 0; i < 10; ++i)
    {
        auto th = std::thread([=]()
        {
            dummyExpensiveBlockingNetworkCall();
        });
        threads.push_back(std::move(th));
    }

    std::vector<int> resVec;
    std::for_each(threads.begin(), threads.end(), [&](std::thread& th)
    {
        th.join();
    });
}

int main()
{

    slow(); //buggy, reuses threads even though it should not.
    /*
    output:
        slow begin, id: 968
        net begin, id: 968
        net begin, id: 3184
        net begin, id: 5076
        netnet end,   id: 968, dur: 10s
         end,   id: 5076, dur: 10s
        net begin, id: 5076
        net end,   id: 3184, dur: 10s
        net begin, id: 3184
        net end,   id: 5076, dur: 10s
        net begin, id: 5076
        net end,   id: 3184, dur: 10s
        net begin, id: 3184
        net end,   id: 5076, dur: 10s
        net begin, id: 5076
        net end,   id: 3184, dur: 10s
        net begin, id: 3184
        net end,   id: 5076, dur: 10.003s
        net begin, id: 5076
        net end,   id: 3184, dur: 10.005s
        net end,   id: 5076, dur: 10s
        slow end,   id: 968, dur: 50.017s
    */

    //fast(); //correct
    /*
    output:
        fast begin, id: 4124
        net begin, id: 2476
        net begin, id: 2684
        net begin, id: net begin, id: 2848
        net begin, id: 4724
        net begin, id: 1048
        net begin, id: 4080
        net begin, id: 1364
        net begin, id: 1776
        3140
        net begin, id: 2000
        net end,   id: 2684, dur: 10.009s
        net end,   id: net end,   id: 2848, dur: 10.045s
        net end,   id: 3140, dur: 10.003s
        net end,   id: 2000, dur: 10.001s
        net end,   id: 1364, dur: 10.006s
        net end,   id: 4080, dur: 10.011s
        net end,   id: 1776, dur: 10.004s
        2476, dur: 10.211snet end,   id: 4724, dur: 10.004s

        net end,   id: 1048, dur: 10.012s
        fast end,   id: 4124, dur: 11.375s
    */

}