Misconception #1: "Offline mode works for me. If you say it doesn't for you, you're lying."
Offline mode doesn't work for everyone and most of the time it doesn't stay in offline mode when it does work. Some people may get it to work for them, but if it was so good there wouldn't be so many complaints.
Misconception #2: "Everyone in the entire universe has high speed internet. If they don't, they're too poor to play games or need to give up or move."
A large percentage of people (which I cannot currently acquire the actual percentage) do not have high speed internet. These people work and pay hard cash (or get the money from hard working people) for the games they play just like everyone else and have a right to speak their concerns and opinions.
I myself only have the option of cable (which is $70 a month, just for the internet alone) or dial-up.
Misconception #3: "People that are against Steam don't make any sense. Steam has only benefits and no cons."
This one should answer itself. If there were nothing but benefits, there would be no discussion about this and everyone would be honky dory with everything.
Misconception #4: "People that like physical copies are behind the times and need to get with the future!"
[img]http://www.gordtep.com/files/2009/08/bttf2.jpg[/img]
This one is just absurd, but actually does come up in discussion. It is kind of broad, as in it deals with more than just Steam, but Steam users tend to say it more often.
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Feel free to add more misconceptions you encounter.
Again, this is not meant to cause flame wars, or trolling, or anything else. I just wish to represent the other side equally. Keep it civil.