Nothing I can say will say something better than every other post, but imo using or as many people will accuse you of 'stealing' a team, is not bad but is for all reasons already mentioned, just good to get used to the tier or find your favorites. I have been harassed many times in every tier by people accusing me of using archived teams, when in fact I have had no success without first using one. There is nothing "original" about using your own team, if that is the argument. You might be using a Standard set, or a set you have seen, or a compilation of six Pokes that has been used before. At this point in the metagame, almost every combination of Pokemon has been used before, at least the common ones in each tier respectively. So, we all technically "copy", but others think it is somehow a sin to use someone else's team, when in fact there is a word for this: playtesting. Duh. So, (1) using other people's teams is not bad, EVER, and (2) people accusing these people of stealing are morons, because the only reason for why it might be bad is to name it as your own.
My personal example of this what I started UU off when Honchkrow and Gallade were still in the tier (not too far off), and I made a team extremely similar to the team xianglongfa has archived. Coincidence or did I steal it? It was by happy chance that I thought: Oh, Honchkrow is dangerous, Raikou is dangerous, Rhyperior is dangerous, and so on and so forth. I put it together, and yet somehow it belongs to the guy with the archived team. There were distinct differences obviously in EV's, sets, etc. but the point is, there really is nothing wrong with playtesting a team, and if you happen to notice: "hey, he is using LR's team" or whatever, there is nothing bad about that, as if they beat you, the team is simply better than yours or they are a better player themselves.