Probably somewhere in between. Pretty good proof exists that it was a common phenomenon in ancient Greece. Good proof also exists that it was used to slur various peoples too.
Probably existed in Sparta. Probably significant, but not as widespread as people think/thought.
Probably does not amount to much of anything and it proves even less. The idea of Alexander "probably bisexual" or ancient Greece's probably tolerance to "homosexual" relationships is interesting in the sense that it reflects what is often the case in a society based on assumptions fed by a popular culture that thrives on innuendo instead of actually searching out the original sources and reading them for ones self and not relying on sixth source information from people who obviously have alternative motives for saying what they do. So the "may be he/they were" shows that for most part the "proof" is nonexistent and without proof one is talking mere fantasy and allowing such fantasy to go unchallenged is the indulgence of fools and mental vagrants....yes I am talking about modern society here.
Here is another food for thought for people out there: What is interesting with this whole subject is that the biggest supporters of homosexuality being openly accepted in ancient Greece is put forth by openly homosexual "academians" such as David Halperin, Gore Vidal, John Winkler, Jonathan Ned Katz, John Boswell and Michel Foucault. It was Walter Pater (1870's a poet and tutor) he and his band of "merries" that just out of a weird coincidence were all homosexuals, originally began this fiasco of a theory in Oxford. We find them introducing a totally new "theory", in which Platonic love has nothing to do with "phyche" but is totally based on phisical attraction. Later we find a list of wanna-be "historians" of Hellinic sexuality, see: Michel Foucault, John Boswell, John Winkler and David Halperin that were or are all homosexuals, strange coincidence once again striving to make some connection between homos and Hellinism. The reason, of course, is simple and I mention it above, similar to those of Eurocentrics and Afrocentrics. Ancient civilizations such as Greece's have always been viewed as a model of civilisation. So what better way to justify their lifestyles than by connecting it to one of greatest civilizations and thus legitimise same-sex?
Another food for thought: contrary to what some would like us to believe, of the inumerable quantity of writings, literature, plays and written records of daily life in ancient Greece and history of the civilization which the Greeks legated to posterity, only a minuscule 5% of writings make some mention about homosexuality. As for painted vases, out of all the thousands of ancient Greek painted vases that have so far been discovered, over 80,000 have been found in Attica alone, that's the prefecture in which Athen's is located, only .02% have an overtly homosexual/bisexual theme on them. Pretty low percentage for a socieity that is so openly homosexual, don't ya think? From the inconsequential evidence available only individuals with alternative motives would manufacture allegations of such an unsustainable nature. Given the narrow selection found of such activities, (i.e. pederasty/homosexual/bisexual) in literature and artifacts, it should be kept in perspective that there is no real reason to believe such activities were the "norm" or representative of ancient Greek society as a whole any more than media distrubution of modern pornography(child, same sex, etc.) indicate what is normal and accepted in modern times by the majority of the population.