A couple of weeks ago Paul Adams, a user experience researcher at Google, wrote a post titled Why “Liking” is about more than just liking which contained the following insight

Why do people ‘like’ things on social networks?

It would be easy for us to assume that it is because they liked the content. But it is a bit more complicated than that. It’s a combination of the content, and the person who posted it.

People sometimes ‘like’ content, not because they actually like it, but because they want a lightweight way of building their relationship with the other person. It’s similar to being in a group, maybe in a bar or cafe, and there is someone there that you’d like to get to know better. They tell a joke that isn’t very funny - but you laugh that extra bit louder, and grab a bit of eye contact, just to build that relationship
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What this means: Just because someone ‘liked’ a YouTube video about Budweiser, that doesn’t mean that they’ll respond positively to Budweiser advertising. It also doesn’t mean that they want to become a member of the Budweiser fan page. In fact, they may dislike Budweiser, but like the person who shared the video. By targeting Budweiser ads, you may do more damage to the brand than good. When targeting advertising on social networks, mining content in the absence of understanding the people relationships is a risky strategy.

I agree that in the context of Facebook, liking a status update or shared link is often just as much about phatic communication as it is about the content that is being shared. In the example from the screenshot, the people who liked the item aren’t saying they like the key terms in the status updat(i.e. hospitality, Tokyo, Japanese, etc) but instead are showing interest in the poster’s news from their trip abroad. When considered, the fact is that the work like actually harms the feature’s use since I’ve seen people want to show some sign of support by “liking” an item on Facebook but then shied away when considering what the word actually means. For example, I was recently a victim of identity theft and I know someone who almost clicked the “like” button as a show of support until he realized he didn’t want people to think he actually liked the fact that I was a victim of fraud.

However Facebook’s isn’t the only model for users in a social media application to show their appreciation for the status updates of others. Both FriendFeed’s like feature and Twitter’s retweet also provide a mechanism for showing one’s interest in another’s status update but also have the side effect of sharing this update with your friends as well. On both of these services, a user clicking on Like/Retweet often means they are interested in the content they are sharing not just engaging in social niceties with a friend online.

In other words, although it may not make sense for Facebook to target against ads to you based on the content of the status updates you’ve liked, it may actually make sense for Twitter or Twitter apps to target ads based on the content you’ve retweeted.