Yeah, they definitely won't do well over non-compressible non-repetitive data, but they can help for situations where the data isn't compressed at rest or where

Yeah, they definitely won't do well over non-compressible non-repetitive data, but they can help for situations where the data isn't compressed at rest or where data is repetitive. Like I said, for many technical people you can roll your own and get reasonably close, but not everyone or every application that deals with large amounts of data fits that mold.