This kind of attack is easy enough to see and correct, assuming that there are lots of people looking. If there aren't, then it's just as easy to unfix as it is to fix, until one party or the other gets bored. Other attacks that aren't so easy to correct are the ones that make unsubstantiated claims that promote minority views, that inflate the importance of individuals or ideas while deflating those of others, or that have minor, hard-to-check acts of vandalism by people who revel in getting their work accepted as fact (eg. changing one false fact to something else, so that if it is spotted it's reverted to the first false fact).
Wikipedia is useful, yes — as a source of references. If you don't follow them up, well, don't quote it for anything important...