From: Tigerm1019@aol.com
Using this line of reasoning, William Shakespeare would be considered a plagiarist. More likely it's a case of two writers using the same very common premise, one far more effectively than the other. It is possible
for
different writers to come up with the same idea or for a writer to be unconsciously influenced by others.
Or consciously influenced. Or deliberately imitative for reasons other than plagiarism. There's a whole slew of reasons why two stories might come out the same.
Newbie writers, unsure of themselves, might be particularly susceptible to what they've read in a handful of zines, especially if they are motivated more by a love of B7 than a desire to *write* (as I suspect many are).
Deliberate imitation might be practiced as the sincerest form of flattery. Probably newbies again. And a newbie writer keen to go with the flow might retread worn ground without even considering it.
Still with newbies, have you ever noticed how newcomers to fandom tend to dredge up chestnuts us old hands buried long ago? Was Blake a freedom fighter ... or a terrorist? And what if Avon had found Vila on the Orbit shuttle? Since a fair proportion of fanfic seeks to resolve unanswered questions in the series, two fans asking themselves the same question could well come up with similar answers.
Two writers with access to the same discussion forum might end up with similar ideas for a story, quite independently from each other. Fandom does sometimes feed off itself, after all.
Two writers, again quite independently, but with similar mindset and areas of interest vis a vis the series (let's say, purely for example, Avon getting off with Cally) could end up writing similar stories by sheer coincidence. And the more popular the theme, the more stories written about it, the more likely that that coincidence will eventually occur.
The more in canon, and especially in fanon, the writer tries to be, the greater the likelihood that he or she will accidentally hit on a plot that someone else has already ploughed through. Stories that reiterate series events as they were shown are even more likely to do so (all Rumours Cellar stories have a lot in common from the start, for example, and unless the writer's going off on an AU tangent, they'll have a lot in common by the end too).
Two writers might, again independently, rehash a plot from another series (like Trek), with a pretty obvious likelihood of close similarity in at least some respects. (It happens outside fandom too - take the SF short story classic 'Arena', the ST ep of the same name, and the B7 version, 'Duel'. Now imagine that two fans both sit up late one night watching the same grainy B&W classic from 1931 on TV, and promptly start on a story about a mad scientist cobbling together the Perfect Human Being in his storm-wracked lab and deciding he's just got to have Avon's Brain).
Deliberate imitation might be perpetrated as parody, though IME such stories tend to be blatantly obvious for what they are. Similarly, stories that deliberately invert the standard tropes of fanfic stand out simply because they're going against the grain.
I'm not suggesting that these things happen all the time, because I think we'd have noticed by now if they were. It's because they're unlikely, but nevertheless possible, that we stand to notice them when they do happen and our suspicions get aroused.
Neil