Bill Simmons was one of the first must reads of the internet. Over the years his schtick has grown predictable but there are still flashes of Brillance such as this response to this question from one of his readers.

Q: Wondering if you could settle an argument between me and my buddies? We
were discussing how many sexual partners Jenny had in "Forrest Gump." Everyone
seems to think the over/under should be set at 250. I argued that it's got to be
at least 500. And that's conservative. Keep in mind she was a hippie, drug
addict in the '60s the time of free love. She was naked on stage playing an
acoustic guitar. She was molested by her father. I'm pretty sure she took down
that whole Black Panther rally. Am I way off here? I'm not saying she's a bad
person. But if a hot girl has sex with someone like Forrest, chances are she's
got a bad case of the "Ben Stillers" -- i.e. she can't say "no." Now that I
think about it, I'm saying a grand easy.-- Keith, Hermosa Beach, Calif.
SG:
All right, let's figure this out. According to Jenny's gravestone during the
scene when Forrest says goodbye to her and it gets overwhelmingly dusty, she was
born in 1945 and died in March of '82. We know that she went to an all-girls
college in the mid-'60s (probably not a lot of sex at that point), that she got
expelled for posing in Playboy, that she did the naked guitarist thing, and that
she eventually became a traveling hippie in the late-'60s, leading to the scene
where she spots Forrest speaking at the Washington Monument and runs across the
water to see him. At this point, she's dating the guy from Berkeley who Forrest
ends up punching in the face; you'd have to guess they'd been dating for a year
or two, and the Free Love Era had just started ... so she couldn't have topped
25-30 partners at this point. We also know that she got knocked up by Forrest in
the 1977-78 range, cooled things down and became a diner waitress to provide for
her son over the next few years -- can't imagine a lot of sex happening for her
from 1978 to 1981, and then we know that she moved back in with Forrest and
their son Haley Joel Osment, married Forrest and died a few months later.
So
Jenny's sexual prime happened from 1970 to 1978 and culminated in her turning
into a coked-up disco queen and nearly jumping off a balcony. Even if she
averaged 40-50 partners per year over that stretch -- which wouldn't have been a
Chamberlain-esque pace by any standards -- there's no way you're getting to 500.
Also, girls who sleep with hundreds and hundreds of guys inevitably start to
look weathered and worn down. As my old Boston buddy Mark Fanning used to say,
"You can usually look at a girl and SEE the number of guys she's slept with."
That's why women don't last long in the porn industry; they're aging in dog
years. So since Jenny looked relatively good even when she returned to Forrest's
house in 1978, I'm putting the over/under at 220.5 and making a guess of 205 for
her total number of partners.
(The bigger question: The movie implies that
Jenny died of AIDS ... and yet, she died in March of 1982, nine months after the
first recorded case of AIDS in the United States. So how did she get AIDS in the
1980-81 range if she was taking care of Haley Joel Osment and working in some
random diner? Could that have been a bigger plot stretch? Or was she still
throwing it around even as a single mom? On second thought, maybe we need to
bump up that over/under.)