I haven't heard anything about this, but I wish you could stay as an amoeba/bacteria like creature and infect other, more developed, creatures like in real life. That would be fun.

You attach yourself to some creature's food source, it eats you, and now you're swimming in its bloodstream popping white/red blood cells. On the other hand, if you didn't develop the ability to withstand stomach acid, you'd lose right there.