They're very much real. They're just like any other rare spawn, usually drop a gold gralat. The reason they're seen so much less is because Swamp Town is so populated, whenever one does spawn, someone gets to it right away.

Had a friend who saw one in Air Asia not too long ago (since blobs did spawn there).

The real myth is the Giant Gold Blob. Now this I've only heard stories about. This is the myth. I heard that one spawned once and some lucky noob got the ultra-rare UFO morph from it.