There's like, 18 maps now.
The reason there's no single player? It's a Multi-Player game. If you wanted a single player game, then buy a console game.
Hackers...Sure, they're a problem. But there's a way past them. However, I don't get your claim of 'viruses', as the game is clean and you can't get viruses from the hackers -.-
Also, you don't have to pay real money. It's free to download, it's free to play. Paying cash for in game goodies is natural, as you'd do it for some console games as well. But it's not a necessity to play. If you can aim and click, then you can play. You don't need a cash gun to play well.