BussinessInsider secured an interview with a "very successfull" iPad developer who experienced first hand the incredible lengths Apple goes to ensure the secrecy of their unannounced products.
The Developer, who wished to remain unnamed, figures he was "probably the sixth person to get an iPad" before the iPad's official release. The requirements to get an iPad early came up short of selling one's soul. Apple took down the social security numbers of the four developers allowed access to the room, on the Developer's company's property, with the iPad . Apple then required the test unit to be viewed in a room with no windows and new locks provided by Apple.
Once in the room the developers were greeted with a prototype chained to a table by bicycle cables drilled into said table. The prototype was then housed in a custom frame to disguise everything except the LCD. Apple went as far as to take pictures of the wood grain of the desk the unit was drilled into so they could trace any leaked photos. The photo above, which was leaked Jan 27, 2010, corroborates many of the developers claims. The iPad in question appears to be as locked down in the same way as described above.
"We could plug into them so we could code to them and we could touch the screen and play with that, but we couldn't see the form factor."