Creative Differences: Players have left in the past due to disagreements regarding how the RP should be handled.
Creator Breakdown: Unfortunately, Real Life tends to rear its ugly head and some participants either drop out to set their lives in order or take a noticeable shift in tone with their posts. Can unfortunately cause a cascade effect when someone's departure is especially messy.
Defictionalization - Pokémon in the RP sometimes go on to become part of a players team within a RL Pokémon game, though a lot of the time this is inverted as well with Pokémon being based on ones from an in-game team. A notable inversion being the GreNinja Squad which started as an in-game team, but a combination of the player liking the concept and the team proving itself to be popular/infamous enough to cement their inclusion in the RP.
Old Shame: The early RP isn't exactly looked at well by most of the writer base that's still around, due to it being much lower in overall quality since it was originally a Forum Game with no continuity.
Real-Life Relative: Gamer and Meddler's players are RL siblings, as are Joseph and Emma Hudson's.
Romance on the Set: At least one couple has ended up in a relationship just like their characters.
Throw It In: Some elements of the RP were created simply because someone did something random and the rest decided it was good enough to throw in. Examples include:
Jane's inexplicable Southern accent at the beginning of the RP being explained as a Hoennese (In particular Mossdeep) accent.
Champloo, Dune's Lucario, decided to make a batch of super-chocolaty brownies. It was suggested that, do to the sheer endorphin-releasing goodness of that much chocolate, they should be able to reduce a Shadow Pokemon's shadow gauge. This is eventually how Vega the Drilbur purified.
Crewe being a Sneasel turned human happened when her player made a joke in the chat regarding a Running Gag... and everyone realized the idea fit in perfectly with her (up to that point improvised) backstory.