There are several reasons to follow someone on LingQ
Suppose you are interested in seeing what they are up to or following their wall posts, shared lessons, etc... In that case, you can follow them and then filter your friends' activity list to only show you the activities of members you are following.
You may be interested in following friends or in following some members who are very active in your study language. When filtering the friends' page by those you are following, you also can see how you are doing compared to your friends in the activity and LingQs rankings.
You can share lessons with all those you are following or with specific members you are following.