The AGOT Tourney rules require a player to turn over all cards in Shadows (for those unfamiliar with the game, that basically means they're face down on the table but not exactly in play yet) at the end of a game to ensure no cards were placed there illegally (and not doing so can result in a DQ). I guess it just didn't occur to FFG to include a similar rule here but they should. Putting out, say, an agenda horizontally in front of a server as if it were ice isn't bluffing. It's cheating.
The Shadows ruling in AGoT is actually the main reason I asked the question. I kept expecting them to address what happened if you installed a card incorrectly, but it was never addressed in the rules. So it got me thinking that given how bluffing is more prominent in Netrunner than other CCGs, maybe installing cards wrong was ok.
Now that you mention it though, installing an agenda like it was a piece of ICE in order to keep the Runner from accessing it is pretty darn powerful. You could never score it, but as long as you never intended to…