To me, likes equal posts that people appreciate, or agree with. It's not just pixels like some people are saying, it's more so the action behind them. Through that single like, you know somebody agrees with you. They respect your post. It's human action in a way, and you can appreciate it as they appreciate you.
Now, having your inbox flooded with them, it's like something you didn't earn, and you just don't feel right about it. And also in the fact that somebody just decided to spam you for the fun of it.
Once again, it isn't so much the like itself, it's the knowledge that another human being, well, likes your post. They agree with you. You know you at least posted something of quality, and made somebody happy or excited or anything, you made them feel something positive. Just saying that, to me, likes mean much more than a simple counter that adds up on my profile. In my eyes, It's the quality of the posts I made, and the other human beings that appreciate the quality. Without that real feeling behind it, it just seems soulless in a way I guess.