The first problem with web serials is that you write your weakest chapters first and release them into the wild.
The second problem is writing too much. I am reading a popular web serial right now to see what's all the fuss is about and all I want is to edit, edit, edit it into something more concise and refined.
Don't write YA novels that are five times longer than War and Peace, please.
I have seen that to be a viable path to publishing many times now, as well as other benefits like building a community of readers.