It's not a big deal to me if someone doesn't follow back when I follow them. But when someone follows me, I will usually do a follow-back. I don't do so because I feel I "have" to though. And I don't want anyone I follow to feel like they "need" to follow me either.
When following someone, I usually set an alert to receive an e-mail notification when they've released a new review because the reviews that I read are only from people that I follow. I used to only set alerts for people who write reviews that I enjoy, but I figured it would be helpful to provide feedback to others who are working on improving, too. (Of course, we are all continuously striving toward improvement!)
By following a variety of people, I have a greater variety of reviews from which to choose in my e-mail inbox. While I do realize I can just go to the Community News page to see the most recently released reviews, sometimes reviews that I want to read "fall off" the list before I can get around to reading them. On the other hand, I can flag the reviews that I eventually want to read in my e-mail in-box. I just figure if someone goes to the trouble of following me and possibly reading my reviews, I'd try to return the favor as often as I can. I can't always read every review, but will do my best to read as many as I can.
The ONLY thing that annoys me about the follow function is for someone to follow you simply for one little point, only to immediately unfollow.