Is it really that surprising? It's no different than walking up to a stranger in the real world and saying, "You know, if you did it this way you ...". You may get a positive response, or you may get a negative one. It's usually more of the latter, though, and I wouldn't blame them one bit. Unless I am seeking advice, I very rarely want any one else's input. Quite honestly, unsolicited advice does border on rudeness.