This comes after a spate of disagreements between the two companies. This bad blood is said to have started when Facebook made an offer to buy Twitter for $500 million in 2008, an offer that was rejected by Twitter on the grounds that the Facebook stock they were being offered was vastly overvalued.
Since then it has been on again, off again war between the two sites with incidents such as the time both companies made an offer on photo sharing application Instagram. The deal was eventually closed by Facebook, who then blocked twitter from making Instagram photos available to view directly from twitter feeds.
Where the next battleground will be for the two social giants only time will tell, but I for one am glad of the conflict, as it ensures that neither company gets lazy and that innovation is constantly encouraged. A perfect example of the merits of competitive capitalism.