BitTorrent's wasn't unethical or shady (unless you think all adult content is shady). They'd licensed the content - which was, IIRC, an kind of free teaser ad for 'LightSpeed' porn - which I remember as being an odd name for a porn site. Caused a huge fuss on Slashdot.
It may not be so much innocence as different cost considerations.
In 1996 bandwidth was at far more of a premium than it is now, so even the modest demands of Google AdSense would have had a much greater cost to the user.
And certainly Hotmail remains slow, though not so much for lack of bandwidth anymore.
The interesting bit here is that that tactic did come back to haunt myspace, but in a different way than you'd expect. The guys that built youtube used the same tactic but by bitting myspace users to come and use youtube.
A quick summary:
Facebook: Spammed Harvard Students
BitTorrent: Free Porn as Initial Bait
MySpace: Spammed >100M on Launch Date
It appears as if (slightly) shady techniques can give you the advantage you need to succeed.