This tactic does not extend to business. You don't 'win' by having the most users, you win by making the most money, and having a wide open market is stupid and dangerous for a company. This is the major failure with Apples 'PC and Mac' advertisements, it doesn't tell us why we should buy a Mac, just why we shouldn't buy a PC. This tactic presently works for Apple because the people who know the difference between a PC and a Mac are likely aware of the pros for Apple, they just need to be overwhelmed by the cons of a PC.
For a new product, your consumers have no knowledge of your pros, and slandering your opponents does nothing except clue them into their failures. The prime example here is again in politics, slander is a tactic always taken by the right-wing parties, however when your claims are hollow and see through they can fail by record numbers. This happened in the UK when Labour gained the majority with Tony Blair, the conservatives launched a slander campaign that not only alienated voters from the conservative party but had no effect on keeping liberal voters out of the polling booths, they essentially handed parliament to Labour. The conservatives here in Canada keep playing the same tactics and have yet to get a majority through their tactics. Again the same could be seen with tactics used against Obama, but they were baseless claims and liberal voters came out in force, conservative voters staid at relatively the same levels but decreased vastly in percentage.