So I contribute FP to buildings unsolicited in order to get the FP and BP. Is this an OK practice? Several times players have replied that I undid what they were planning, and I shouldn't do it...
In a nutshell, it is a personal decision. "sniper" or "snipe" is a bit if a misnomer and carries a negative connotation in FOE. Well, it is kind of negative in RL too, if you are the sniped. INNO allows anyone to contribute to a GB of a 1: Friend 2: Guild Mate 3: Neighbor. They have never stated it is cheating, sniping, stealing or whatever term du jour to describe contributing FPs to a GB. Nor have they ever stepped in (AFAIK) and prevented it.
Whether you want to engage in this method is solely up to you as long as you understand the benefits and consequences. Most guilds do not allow it between members of the same guild. Many friends do not appreciate it nor allow it. Many neighbors do not appreciate it nor allow it. Personally, I would ask guild leaders what their policy is, if it is not clearly stated somewhere. As far as friends go, some populate their friends list with self-levelers and "snipe" them regularly, since that friend allows it. Rule of thumb is to not contribute FPs to friends or guild mates GBs, unsolicited, with the exception of those who welcome it.
As far as neighbors go, it is up to you whether you engage in "sniping" or not. Just beware that some are very math challenged and ignorant to how the game works and demand that anyone who contributes to their GB, would ask them ahead of time or at least contribute an amount they preconceive as fair. Meaning? You may provoke them and you may get a barrage of nasty responses from them, threatening your life and limb and calling you names that you may have to look up in an online dictionary and or wonder how they expect you to do the things they mention. I mean, some are very graphic and explicit and may cause your mind to wander and wonder how, what they are suggesting is even possible. As long as you know what you are getting into and can withstand those type of attacks, you are free to make your own decisions.
So, if you so choose, snipe... ahem... contribute away.