Hacking votes has long been a problem on HN. It's well known that if you can collude to get enough votes in the first 10 minutes or so of your post, you can make the front page and continue to get votes based on interest. Without a hack, it's likely your post will barely get seen by anyone to even get voted on.
Not exactly.
1) If there is voting collusion, the point counter will increase, but the points won't "count" to getting to the front page. (upvotes to posts which come from a non-HN referrer are automatically discounted)
2) Flagging is much, much more powerful than the effect of upvoting. If a terrible/advertorial article makes it to the HN front page despite collusion, it will die quickly as the increase exposured draws flags.