There are plenty of things to argue about on the internet. Sometimes it is surprising that more people do not get paid to do so. The bigger debates always seem to stem from issues of loyalty, most commonly to a brand. The first thing that will come to mind for many will be the Mac vs PC debate that will rage on until the end of man, but there are other instances of this.
From what I can tell, people argue the most about software preference, religion and politics. This may be a bias that comes from the fact that those discussions annoy me to no end, but that is doubtful. The unending nature of the talks, which always turn into shouting matches, is mind boggling.
If people disagree at the beginning of any one of these discussions, they are very unlikely to agree at the end. It makes one wonder if these discussions are started out simply to produce conflict and never anything positive. People can feud for eons about which is better, but there are many things in the world that are terrible for you and great for tons of other people.

One Comment
This is so true Amber. I make it a habit to avoid the flame wars. If I disagree with another about a like or preference, so what? Those differences are a part of what makes life exciting and unpredictable.