Why not invade the top buff every time?
I've been invading the top buff every time in normals after my first camp and it always worked so far. Every jungler seems to start bot so I just get a free Red/Blue and even Krugs/Gromp before they get there. I don't think the Gromp/Krugs->Buff->Buff route is popular anymore so there's almost no risk. Even if they find me, I just smite it and run away (flash if need be).
If I'm playing a jungler who is pretty useless pre-6 and lacks escapes, I don't usually do this since it is less efficient farm. However, for more early-mid game junglers, I don't see much of a disadvantage - especially if I'm against a similar jungler who wants to snowball lanes early. I also don't see much of a counter if their normal path isn't the one above. I might be wrong, but wards tend to expire by the time I get there and no one really starts a pink early.
So what's the big downside to this? Why aren't more people doing this?