This is the normal spam, where people post adverts for their companies as comments on your blog. Though still a nuisance, it is becoming more rare, since it can be combatted. Here is the advice from King’s on dealing with it.
Since comment spam is being overcome, people are turning to other means. One is to simply click ‘Like’ on your posts. The thinking is that you will investigate and see who they are – so it advertises to you.
One thing you can do is turn off Likes for a blog post. While writing/editing a blog post (at least through the Dashboard), there is a “Show Likes” setting that can be unchecked. This will prevent the “Like” button from appearing on the post itself and on the admin bar that logged users have. It won’t let you pick-and-choose who is allowed to “like” and who isn’t, but it will prevent “like” spam.
However, you are losing the “like” feature on your blog. Source: http://en.forums.wordpress.com/topic/followers-spam?replies=13
Here’s some of the nuisance ‘like’ spam that I got in my email shortly after setting up this blog:
Of course, it is possible that they did like my blog. But it seems a coincidence that they all have their own businesses to promote.