"Second Life is supposed to be about limitless opportunity," [Hunter] Walk remembers them thinking, "but you can't be a 10,000-foot dragon. We stood back and we said, 'Wow, this is Prisoner's Dilemma.' Like the first time somebody wants to be a 150-foot giant, then everybody's going to want to be a 150-foot giant, so all of a sudden you're in this out-of-whack world."So they set what they thought were reasonable limits on the avatar (according to the book, there's an eight-foot limit on height), so that going beyond those limits requires attachments... which don't work and play well with some things, but perhaps LL thought that a good thing, to further discourage a height arms race.
Ironically, though, SL itself fosters height inflation. Unless things have changed drastically since I went through orientation, you're left to set your sliders with no feedback whatsoever about what those sliders mean. I'd love to see an indication of the equivalent in cm or inches of the slider settings for sliders that correspond to spatial dimensions, but even one of those textures laid out in squares that one could stand in front of at that point in orientation would give newcomers an idea of what they are getting.
I expect that very few people will choose the extremes if they know what they're getting--otherwise, there's an inclination to choose something in the middle--and I'm pretty sure that, for women's avatars at least, that's well over the 5'4" US average woman's height. (And ironically, the slider settings don't even encompass the variation in body part size in RL. Robert Wadlow and Zeng Jinlian, for example, couldn't have made their avatars resemble themselves.)
(May I take advantage of the chance to ask once again for you to consider voting for VWR-1258? Thank you.)