Researchers in Germany released a pair of papers documenting severe power analysis vulnerabilities in the bitstream encryption of multiple Xilinx FPGAs. The problem exposes products using FPGAs to cloning, hardware Trojan insertion, and reverse engineering. Unfortunately, there is no easy downloadable fix, as hardware changes are required. These papers are also a reminder that differential power analysis (DPA) remains a potent threat to unprotected hardware devices. On the FPGA front, only Actel seems to be tackling the DPA issue so far, although their FPGAs are much smaller than Xilinx's.
Slashdot @ http://it.slashdot.org/story/11/07/21/1753217/FPGA-Bitstream-Security-Broken
...could be bad news for FPGA miners alike...
Not really, unless you're looking to profit from a proprietary design... All it means is someone can copy the design off the hardware. Since the prominent FPGA design is open source, this is not really a threat.