Have you found such accounts already?
No

I am just developing this software and not running it myself.
There are nice calculations that a safe passphrase can't be cracked in million years but is this still valid if thousands of people use such tools and the tools getting better?
The thing is, that we are not targeting the "real" accounts with 256 bit private keys, but the HiberNXT accounts that only have 64 bits of entropy. This way there are dozens of public/private key pairs that match the wanted account number.
I have no calculations how long this would take, though. Let me do a quick "math".
64 bit means basically 18446744073709551616 different tries. On average you would need half that much.
Let us assume every one has 10 computers which do a total of 150.000.000 tries per second. Further lets assume we have 1000 users using it. This would mean on average, after 10000000 seconds an account would be cracked. Most likely a lot faster.
I am sure we can make this software a lot better, so we can get closer to 1000 or 10000 seconds. You must understand the current GIT status as the first proof of concept, from where we can start improving.
NOTE: This calculation is for 1 Account only, as we have around 15000 Hibernxt accounts, it would take 10000000/15000 = 600 seconds to hit any one of them. It is pretty fast imho.
TODO: At the current stage, the software is not able to check for multiple accounts simultaneously. This fix should be a quick one though. Feel free to forge and hack.