A lot of people want to use this term differantly, but it has one specific meaning, with which it was created in pop culture and then moved on into real world use.
"The Friend Zone" is an ironic, negative, term for someone who pursues someone else with deceptive, sexual intent, but then gets frozen out without a direct rejection. The stereotype being two predatory dudes in a bar talking about their conquests and the girls they are chasing, and asking each other for status updates, and a failure without a crack up or rejection is "oh man, you got Friend Zoned... ouch!".
To put it bluntly if your okay with being someone's friend or that was the intent to begin with, then it's not really being "Friend Zoned" as the slang was intended to be used.
Whether the person being chased does it intentionally (being onto the person in question) or not (just not interested or getting it) is irrelevent. Typically in cases where it applies being "zoned" is a sign to move on and chase someone else.
In romantic comedies and such someone falling for someone they were pursueing and got "zoned" by (for all intents and purposes) is a typical plot, with differant variations based on whether it happened intentionally or not.
As far as whether guys and girls can just be friends, the answer to that is yes, without the issue of romatic rejection ever coming into it. To put it into a nerdy context, which I'm sure some people here might have had experience with, let's say your recruiting for a PnP RPG group, you put up a paper at the local hobby shop, social board, or whatever else looking for people to game with. A girl responds. This does not mean "OMG, there must be some romantic implications here, unless there is something wrong with her" just because, sometimes you just want someone to pursue a common interest with. Likewise sometimes in doing things like that, you wind up hanging out with girls (perhaps quite a bit) who are already with someone, or whatever else. RPG gaming can be replaced by any other interest where you meet or involve other people.
In general confusion on these subjects seems to mostly occur when your dealing with people who amazingly manage to be even more anti-social than me. You talk to co-workers, maybe hang out with some of them after work, meet people through hobbies or whatever, it's very easy to wind up with friends of the other gender where there was no romantic interest or intent at all. "Zoning" only applies in cases where there is a predatory ulterior motive to begin with.
As far as people making excuses about failures to pursue relationships, well I don't think most people are sociopathic enough to need some kind of blame reversing excuse or whateve as a matter of course. Usually when people get pissed about something like that, there is something more to it, like say a dude being lead on and then "zoned" knowing the guy is going to drift off once the girl gets what she wants. That tends to piss people off, and there is no real recourse for it... and of course there are men who use girls the same way.
In these discussions I notice a lot of people talking about teenage boys "not getting the signals" but the thing is that in a lot of cases they do get very intentional signals that are being sent, and being boys get unusually upset when they are manipulated. The high school years seem to be a time when a lot of girls like to mess with guys that way just because they can and it makes them feel powerful.
I'll also say that people keep mentioning Taylor Swift, but honestly I don't think she's a good example since your pretty much using a stage persona meant to cultivate a specific image and product for sale as the basis for real world relationships. Trying to make any kind of life desicians or judgements based on her songs, or those of any artist for that matter, doesn't strike me as being a wise course of action.