User generated content (UGC) is an increasingly important part of the Internet with some of the largest sites, such as Wikipedia and Youtube built entirely from this media. The disadvantage with User Generated Content is that for disciplines which require a high level of skill and/or technical understanding, such as level design and 3d modelling, the barrier to entry prevents the majority of users from participating.
User mediated content (UMC) lowers the barrier to entry, by allowing the user to pick from a set of content generated with PCG techniques. As they gain a greater understanding of the range of choices, the user can tune the content available by altering the PCG parameters more directly, without having to understand the underlying algorithm.
This method harnesses the strengths of human perception and selection criteria, with the strengths of computer processing power and procedural computation and can take advantage of distributed intelligence such as used in the ESP Game to make the most favoured content widely available.
Examples include Dryad which presents a range of trees which the user can pick from and Spore, which uses this method for all in-game content.
PCG Wiki References
External Links
User-generated content - Wikipedia entry for User Generated Content
User Mediated Content defined in The Death of the Level Designer.