People say that IQ is only a measure of how well people can answer intelligence tests. Indeed, I'm not suggesting that if people were to take a commercially-available test tomorrow, people would necessarily score a particular number. I'm envisioning a score based on a hypothetical ideal intelligence test, which tested not just the traditional measures such as logic and inference but all facets of behaviour that is generally considered clever, smart, brilliant, capable or genius-like by modern society. I also envision that this test would take about two weeks to administer, all participants would get (say) eight weeks of practice beforehand and some suitable motivator would be applied (maybe a different one for each person...?) so people really did perform to the best of their ability. Definitely a hypothetical ideal test.
It's also worth pointing out that the figure of 125 is based on a standard deviation of 16 points, which is the standard measure used in the US and on the BBC's televised tests. (UK Mensa traditionally quote figures based on a standard deviation of 24, so the average there would turn out to be 135+.) This means that I think the average person on my Friends list is about one and a half standard deviations above average, or brighter than about 93% of society in general. You're not "one in a million", but you are pretty literally "one in fifteen". I also use "average" very generally; the arithmetic mean and median shouldn't differ much, though I'd guess the mean might be a shade higher than the median.
What does this mean in practice? It means that (almost?) all of you are smarter than most, most of you are more intelligent than pretty considerable swathes of the population, a sizeable minority of you are brighter than everyone they'll meet on the streets most days of the week and there are a few scary (but nice) freaks of nature as outliers who I tentatively estimate at somewhere over IQ 155 - a good three and a half sigmas above the mean, or at least 1-in-4,000 rarity. You know who you are; keep quiet or I'll be forced to explain just why I think you've demonstrated you're so clever. ;-)
Happy 0th birthday to Jonathon Avi Tandy and many congratulations to his wonderful mother, heidi8.