When Facebook officially launched their updated Like button in February, there was an immediate jump in the amount of referral traffic generated from Facebook.com (as shown in the below graph). In the past two months however, the trend appears to have reversed and the overall percentage of referrals has dropped significantly.
This may indicate that the novelty of the feature has worn off, that users are becoming “immune” to the button so that it no longer registers, or that there is less perceived value to the function. It may also be indicative of growing discontent with Facebook overall, especially in light of flashy new networks such as Google+. Definitely a trend to keep an eye on.