I own a Nikon D7000 and also got an Sony HVL-F36AM flash from my old Sony Alpha 100. Is there a way to use the Sony flash with the Nikon D7000 in wireless mode? Or does Sony somehow block its flash so it only work with Sony DSLRs?
The answer is: no, this won't work.
But it's not because Sony actively is blocking the flash from working. It's just that Nikon's wireless TTL system (which they call "CLS" — Creative Lighting System) isn't compatible with Sony's wireless TTL protocol, which they call "WL" (presumably for WireLess). The concept is the same — a measurement preflash, and then the control flash on the camera sends a digitally-encoded optical signal telling the slaves how much power to use and when to fire. But the implementation of the signal is different (and proprietary), so the two brands can't talk to each other. The same is true with Canon, Pentax, and Olympus's wireless flash systems.
The Sony flash's wireless capabilities are limited to this WL system; it does not have non-TTL "digital slave" mode, so you can't use it that way either. (If it did, you could set flash power manually and still get basic wireless functionality.)
However, you could spend some money and get a radio-based third party wireless trigger system like the Pocketwizard , which you can hook to the flash with an adapter. Many people find the radio systems superior to the optical built-in systems, but for a wide variety of cases the built-in systems are great. (Less bulk, and of course less to buy, and TTL operation, which is available through the higher-price radios but not the budget ones.)
Nikon's CLS flash lineup is excellent (and widely regarded as the best optical TTL slave system). So, while the bad news is that you probably can't easily make great use of your existing flash, the good news is that you won't go wrong in the new system.