NSA would be foolish to go through all the effort it takes to place a back door into OpenBSD. I find it funny how people focus on potential back doors in software and completely ignore that all this software is executed on micro processors that are made by a select handful of US companies. We also have no idea what's really going on in peripheral components of our computers or in networking hardware.
Use OpenBSD if you want to keep out the common criminal but don't fool yourself that you can outwit three letter agencies with your laptops.