Here's my opinion.

If duplicate answers arrive within moments of each other it's not really that surprising. It's the [fastest gun in the west](http://meta.stackexchange.com/questions/9731/fastest-gun-in-the-west-problem) syndrome and very similar answers are bound to occur. 

However an **identical** answer several days earlier like the one found [here](http://askubuntu.com/questions/882298/testing-of-php-fails/887874#887874) I consider a problem. In this case it may simply be that the user requires some guidance on using the site rather than the blatant rudeness it appears to be on the surface. I do think late *identical* should be deleted in favor of those that came before them, however similar answers that are more cohesive or fully formed should be left to the voting process.