Although Pokemon Go's Easter Eggstravaganza is over, fans have discovered a major change to one of the game's core mechanics. It appears that wild Pokemon's stats are now randomized for each player. Basically, multiple players can catch the same Pokemon at the same place at the same time, but discover that the Pokemon's movesets and IVs (secret stats that determine a Pokemon's relative strength compared to other Pokemon of the same species) are different for each player.
Before the Easter event, multiple players could encounter and catch the same Pokemon in the wild. If two players encountered the same Pokemon, the Pokemon would have identical stats and movesets (save for CP) no matter what level the two players were. Now, it appears that IVs and movesets are determined based on level and are only determined when a player encounters a Pokemon to try to catch it.
There are some limitations to the new spawning mechanic. The randomization only seems to occur for players Level 24 and lower, so players that are Level 25 or higher will all encounter the same Pokemon (that is, a Pokemon with identical IVs and movesets.) A Pokemon's CP and level will also be the same for any player that's Level 30 or higher.
So what's the reason for this change? Well, the change effectively stops any third party tracker from identifying a Pokemon's IV or moveset. Previously, spoofers could use tracking systems (which used automatically generated low level accounts to work) to find a Pokemon with perfect IVs or the ideal moveset and then use a GPS spoofer to go to that location and catch it. But with random encounters, trackers are only good for finding Pokemon....not revealing what sort of stats it has.
It's also been pointed out that the new mechanic is similar to how Pokemon Go determines whether a Magikarp is Shiny, which could point to a wider release of more Shiny Pokemon. However, it doesn't make much sense for Pokemon Go to do a mass release of Shiny Pokemon...at least not until the next event.
This could be the spoofing solution that Niantic was hinting about earlier this week. We'll have to see if there's any other big changes to Pokemon Go in the weeks to come.