They say back stabbing is bad in politics but it sounds as if techie companies could give the political mud-slingers a run for their money.
Investor's Business Daily posted the top 10 tech rivalries with commentary and, interestingly, Google is at odds with three of the contenders: Facebook, Apple, and Microsoft. Out of the remaining seven, the New York Times vs. Huffington Post rivalry is interesting to me as a blogger: old media vs. new media.
Others listed include Time Warner vs. Netflix, Amazon vs. Apple, Verizon vs. AT&T, Activision vs. EA, Oracle vs. HP.
For comparison, here's IBD's 2010 top 10 tech rivalries list.