The Problems with Peer-To-Peer Networks

     I've been working on some computers lately, and something I've noticed is the recurrence of people using Peer-To-Peer, or P2P for short, networks.  I can't stress enough that the reason these computers are having to be worked on is because of these P2P programs(heretofore referred to as clients).  P2P clients are a virus programmers best friend.
     Now, before I have people up-tight and yelling at me because I am deriding their favorite free music client, I'll write out for you why these things are so bad for your computer.
     The concept of a P2P network is implied in its title, Peer-To-Peer.  These client programs create a direct link between two peoples computers so that they can share files with out obstruction.  This is and always has been a bad idea.  Opening a gateway between two computers when you do not know the other person is an open invitation for viruses, because you have no way to control what the files they are sending contain.  Also, this open connection that you have willingly created leaves a port open that is normally closed on your computer, typically port 6346 for LimeWire (if you haven't manually altered the settings), and this leads to unpredictable problems. 
     The more ports that are active and unchecked on your computer the harder it is monitor and protect them, that's why we use firewalls.  So, when you open another port using a P2P client, you get a higher risk of people infecting your computer.
     My suggestion is that you shouldn't use P2P clients at all, but if you feel like you have to, use a bit-torrent client like Vuze and seek out a valid torrent file(Without using Vuze's built in search function), rather than using P2P clients like LimeWire and Kazaa. (Though I would like to note here that I am not an idiot for anyone with tech savy reading this, I do realize that LimeWire uses bit-torrent as well.  Its in how the program is structured that I am categorizing it along with crap-ware like Kazaa.)
     But once again, I restate, don't use P2P clients if you are worried about virus infection, they are just open invitations for invasion.  Just go to legitimate sites and purchase files legally, unless you know that it is a file you are supposed to be receiving via a torrent.  Then its okay.