Those are all good points. The Powers of Baseball That Be decided after the strike in the mid-90s that cancelled part of a season and the playoffs and World Series, and made baseball anathema, that something had to be done to win back the fans. So, they juiced up the ball and did all those other things.
It isn't just Bond's 73 homers, but how many guys are hitting 50+ homers now in a single season. It used to be getting 50 was a significant feat.
But in Bonds case there is another factor, too: The new Pac Bell stadium. Candlestick had all those swirling winds, some of which were strong enough to blow Juan Marichel off the mound (remember that? ;-) ). Are the winds in Pac Bell different? Just asking, as that could be a factor, too.
It wouldn't be totally surprising if there's some 'collective improvement'. Take a look at a pinball machine today versus one of twenty years ago; back then, getting a replay on many of those machines would have been considered difficult, but many players today would be able to do so with ease. Best I can figure is that many pinball players today are more skilled than twenty-five years ago (because many modern machines demand it).
obBrags: On a game called "Cybernaut", I once racked up nine credits while still on Ball Two. I'd already hit 9,999,999 and walked away from the machine. When I revisited in 1994 a Pin*Bot (a game I'd found playable but not terribly easy) I managed to score 27+ million (was disappointed nothing new happened the second time the score rolled over; I'd never rolled it over before). I liked Warlok, maxing out the bonus and scoring specials was pretty easy.