Creating AND USING your own cipher is nearly always a bad idea (for typical non-security-clued developers, in particular, who are the ones most prone to this). Designing and analyzing one can be a fairly interesting and/or educational process (and all part of the process of public crypto research, which is what this is about).

Developers, by all means, should use AES and not some random unproven cipher. That does not mean new ciphers should not be designed and analyzed.