Speaking as someone who has done translations with no honorifics to ones where I don't even translate "onee-san" my general philosophy is this:
Judge the audience that will be viewing the subs and translate in a way that minimizes audio-visual dissonance.
I.e. If the majority of watchers are used to honorifics in subs, and they hear an honorific they are familiar with but don't see it in the subtitles, that can distract them. (An opinion already voiced in this thread above).
Some honorifics have quite direct translations and should almost always be translated (like, say "-hime"), but others like -san and -chan (when used normally) the correct "translation" is often simply omission. This can cause significant audio-visual dissonance depending on your audience.
For example, in my translations of shugo chara who is watched by fangirls that like to squeal "kawaii!" around their house, I pretty much keep all honorifics intact, but for Tegami Bachi I avoid honorifics in most circumstances as they are rarely used in the Japanese way.
My opinion on dubs is that with no chance of audio-visual dissonance honorifics should be omitted in almost all cases. The only exception I would make would be for a show that took place in a historically accurate period Japan setting (like heian or edo period, say) where adding honorics to the english dub would help lend it the appropriate Japanese flavor...