Yes, you're paranoid. A drone doesn't need to map out a museum before lobbing a missile at it. An autonomous vacuum cleaner, on the other hand, would probably love to know for sure that it has covered the entire surface.
Personally, I'm imagining a little ball that I rent from the hardware store that rolls around my house for an hour and spits out the blueprints of my house so that I can feed it into a VR program for choosing furniture.
Coincidentally, for the latest Roomba (the 980), we did have a camera on the robot which did visual SLAM for precisely that purpose...the idea being it would map your house while it went, and if it needed to stop for a recharge, it can go back to its dock for a recharge, and then resume cleaning right where it left off.
https://www.technologyreview.com/s/541326/the-roomba-now-see...
We also worked on a remote presence (teleconferencing) robot, which used SLAM to map the building it was in, so that a user could just click on a location on a map or schedule the robot to be in a conference room for a certain time, and the robot could autonomously drive there without someone remotely controlling it. It's a very cool technology that has a lot of really useful, non-scary, applications!
I've tested it briefly, and it seems fairly accurate as long as you follow the instructions.