Actually
That largely depends on context; I both study at an arts faculty where a large portion of students are either openly, semi-closeted or closeted (but, in any case, very obviously) gay and have many gay friends (who, in turn, also both have gay and straight friends themselves, though, in many cases, those are disproportionately gay in number) from all quadrants of life, so I sometimes feel the need to come out publicly and announce my heterosexuality, with various degrees of subtlety or straightforwardness, depending on the orientation make-up of the group I'm currently socializing in.
You know, though I am openly a straight ally (which should be a self-explanatory, but if it isn't, feel free to google that) and do not feel any revulsion whatsoever at having physical contact with gay people (yes, I'm talking about hugs and, if that suits our fancy, kissing on the cheeks just as I'd do with a straight friend of the opposite sex), newcomers may not have been briefed of that fact in advance, so I may wish to signal myself as avaliable to the opposite sex and unavailable to my own, both to not miss out on potential matching opportunities (when I'm unattached, at least, and it came to my knowledge that in more than one occasion, much after the fact, some girls had it all wrong about me

) and to avoid awkward moments of unrequited passion (my behaviour is not always the most heteronormative anyway, which most definitely could lead to confusion towards people with bad/broken gaydars).
Makes a bit of sense, no? YMMV and, in your case and judging by your discourse, I'm guessing most of your friends are heteronormative and either straight or closeted, so you likely wouldn't have to go around telling everyone you are straight.

While on that subject, and also judging by the sheer amount of gay people I know (not just from said faculty but, as I said, also from other areas completely unrelated to the liberal arts), I guess that if every closeted person was to come out at the same time, it would most definitely become handy for straight people to (learn how to) signal themselves as such. Anecdotal evidence tells me that while LGBTQA people are definitely a minority, they are probably not as small a minority as the bigots (many of whom may be closeted themselves) make it seem
And, for that matter, heteronormativity is just a social shackling device, useful only to keep lazy/shy/fearful/hateful (pick your group) heterossexuals from having to, you know, having to say every once in a while, I'm not gay. As if that was *that* hard or awkward a thing to do, anyway
Anyway, I digress
Good on Tim for coming out! As someone posted before, I wonder how Apple will fare in, say, the Middle East (though I believe the high-ups over there, with some of whom Tim already met, already had suspicions and just didn't care either way, as money speaks louder than sexual orientation anyway

)
That fact alone makes this all the more relevant; it very much fits in with the doing [mostly] the right thing ethos so characteristic of Apple.
All in all, I believe the net effect for *everyone* involved and affected (Tim, gay people in general and Apple as a company, including duh its employees, suppliers, customers, etc.) will be greatly positive.