Actually, I think twice raises a valid point here.
In my opinion, there is a big difference between creating a logo for practice and creating a logo for an existing company/product. Fist of all, the process is entirely different. When creating a real mark, you have to (or at least should) go through some kind of a brand audit to understand what the company stands for, what their tone of voice is, how they want to be perceived in their market. For big companies, this includes surveys for the company itself (on all levels) and surveys for their target audience. This then results in a bland blueprint, that outlines all these aspects in a clear way. Then this has to be absorbed by the designer and ultimately translated in a visual style that matches this in the best possible way.
Secondly, when designing for real companies, you can create beautiful work that doesn't work for that specific company. This is something that is of no concern for practice logos.
So for fictional logos, it's about the design and the thinking behind it, without having to worry how it fits the company/product or how the target audience will perceive it. And you don't have to present/defend it in several presentations and possibly go through several rounds of adaptations without loosing you passion to still come up with the best possible solution that you and the client feel good with. A big difference, in my opinion.
I am not saying that the "fake" logos posted here (I posted some myself too) are less valid or beautiful, and they definitely should be showcased here as a great source of inspiration for other designers - as theartist mentioned. I also don't think we should split up the gallery into "real" and "fictional" work. But I feel it would be good to mention what the work is: a proposal for a real job, a chosen logo for a real company or an exercise of ones skills. And if it's for a real company, please add some background information (at least what line of business the company is in).
Just my 2 cents..