My pet theory is that >80% of all posts that hit the front page have been votehacked up there. The first few upvotes are just too influential - why wouldn't you have a dozen alt accounts to give your good/great post the initial boost?
Because that will get you banned like Unidan, if they are from your IP or obvious sockpuppets. Vote manipulation is against the rules... if the admins pick up on it, which they might if you are a high karma account. If others do it for you it is still vote manipulation but not sure how would they ever figure it out.
Unidan is the exception, not the rule. I think that the number of posts and number of competent admins are so out of balance that they can't catch companies like 'HackPR', or even just regular clever people. Maybe they have a few algorithms to catch the really obvious manipulation, but you can work around IP problems with a VPN, work around 'new, no karma' accounts by reposting from a year or two ago, et cetera et cetera.
I agree unidan is not the rule but there have been many others like him who use sockpuppets that get caught pretty quickly. Happened to a high karma EarthPorn mod who apparently only upvoted himself 4 times. You simply do not hear about them because they are not reddit famous. I used to be very active in reportthepammers so have seen many fairly sophisticated tricksters and spam/upvote rings that got caught. Coordinated new, no karma accounts are easy to spot. It gets much more complicated than that. My main account, which I used to mod a couple of defaults and a bunch of others with and that's about it publicly, was banned after I started privately raising shit about the way they were treating employees. Not even vote manipulation. They didn't shadowban me but changed my password on that and a couple of accounts I was using through different IPs (but were obvious sockpuppets). I have never heard of that happening before or since. I didn't mind though; I was just pushing them to see how far they would go instead of quitting quietly. So it can happen to anyone.
Especially when you time it right - there's even sites that calculate the best time for you. I recall reading somewhere that the first 10 votes matter as much as the next 100, as the next 1000, etc. It's almost begging to be gamed.
Quick upvotes are huge. /r/CenturyClub and associated reddits for high karma holders make it a hobby of gaming the system. They discuss timing strategies, keywords, follow each other to get quick upvotes, etc. They take karma very seriously. Most of those people are comment karma whores though who just hang out in askreddit/new and shitpost puns and jokes. Most post karma whores do it through sheer volume. If one in 20 posts sticks that is good enough for them. That is how people like GallowBoob became so popular and now he has so many followers that almost everything he posts gets tons of votes. He only has 4 posts in the last 7 days with less that 1,000 ups and most with far more, up to 100,000+. My one "top link of the day" was posted at 7 p.m. PST so only had 5 hours to get votes. Bad timing. But is was about the first federal court of appeals decision that taping of police with your cellphone was legal. Very sexy keywords for redditors.