This is the MD5 Hash of an empty string:
d41d8cd98f00b204e9800998ecf8427e
This looks like too complicated and unpredictable password.
But, if you search this string in google, you can receive a lot of results regarding this word.
Have you seen it elsewhere?
Well - that is one of main reasons why password systems should not use unsalted hashes for password storage.
hash(password) = bad
hash(password+salt) = better
HMAC_hash(password,salt) = even better
Better yet use salt and dedicated key derivation functions: bcrypt or [url=http://www.tarsnap.com/scrypt.html]scrypt
There are various reverse MD5 sites. Basically, databases of passwords and their MD5.
Like this Reverse MD5 hash lookup
You would find the MD5 for an empty string and many more on these sites.
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Hash is some sort of a one way encryption…it is not easy to retrieve back the original value