Source code for the Carberp banking malware kit is leaked online

From the article: And, as a result of this leak, it wouldn’t be a surprise to see the malware split into numerous different strains, as rival hacking gangs adapt the code for their own malicious ends.

This is the same "fragmentation" argument often made about Android or Linux or indeed, any open source software.

Has anyone ever checked that this prediction (for malware) ever comes true? I'm just a little bit skeptical of such a sweeping, unsupported argument that also keeps source code hidden from the people affected by it.