The published algorithms are prune to dictionary attacks. If you can have even a not too good cryto-algorithms, whose logic is kept really secret you are much secure.
Let's say a hacker, some how got into some non-secure services with good amount of user. And found out the username/password are not encrypted or hashed at all. He can use that list a dictionary. He can also have MD5, SHA1 hashed calculated. The same hacker got it into your secured service, who already have a dictionary to try on. He can get password from MD5 or SHA1 or any known hash, in O(1) using hash-table lookup. Normally, hackers now-a-days have the dictionary to try on, it is just the SALT and hash-algorithm is unknown to them. So, the security measures can be:
1. Protect password Hashes from theft. 2. Protect salt from theft. 3. Protect hash function from theft.
Try to protect them all. All of them can stolen, but probability of 3 theft is less than 2 theft. I agree with Dave, only if he has plan to keep hash function secret. I should not shipped inside java script, so hacker don't need to do any effort.