No, the OS is set to, by default, say "this application is not signed and hence not trusted", it's nothing to do with spreading FUD, it's a legitimate security device –warning users not to run random things that they don't know the origin of.
Not to mention the fact that, although I don't know about Linux (but I'll bet at least Ubuntu does it), but both Windows and OS X have be putting u pat LEAST a "first launch" warning dialog on ANY "downloaded" stuff for several years now, and for the most part, users don't find those things an impediment to downloading stuff in the slightest. In fact, those were instituted to "catch" stuff that might have been SURREPTITIOUSLY downloaded and installed by malware.
And yet nobody claimed that THAT had a "Chilling effect" on downloading and installing stuff from the intarwebs.
What's the big deal here? Heck, Apple even put the default at the "medium" setting, where it would bother regular users the least, and yet still not open them up to every prison-raping, just because they got "click happy" at the wrong time...