PCGamesHardware.de is reporting (Google translation here) that Intel Skylake CPUs may be damaged due to pressure from some third-party heatsinks. Some users have reported bent CPUs and even bent socket pins. The site says the cause for this problem may be the thinner substrate used in Skylake CPUs.
Several manufacturers have issued statements about the problem. Scythe says that coolers using its HPMS mounting system (which include the Mugen 4 and Mugen Max) may damage CPUs if the system suffers strong physical shock. The firm is offering customers a free set of replacement screws. EK Water Blocks' current-generation PreciseMount system should prevent damage, but the company does not recommend that modders use its older water blocks in Skylake systems.
Silverstone states that its current lineup of CPU coolers is designed to meet Intel's mechanical specifications, but is nevertheless checking to see if its older models are safe to use. The company claims it has yet to hear about any problems, though. A similar sentiment is echoed by Thermaltake, which says that most of its CPU coolers include a security system that prevents users from overtightening the screws. The story is pretty much the same with Thermalright, Arctic Cooling, EK Water Blocks, and Noctua, which all state their coolers are safe to use.
It's worth mentioning that nearly all the companies recommend that users remove heavy CPU heatsinks before transporting their systems in order to prevent damage due to shock and vibration.