I'm just wondering, why does some accounts only have 1 reputation?
That is, what causes you to be temporarily suspended? I've looked at the "A day in the penalty box" blog post, but I don't really understand.
Moderators put accounts in the 'penalty box' when a user is not responding to requests to improve their behaviour or when they have been caught cheating the system. That way the rest of the community can continue to provide great questions and answers without having to deal with someone who is causing others distress.
You are expected to think about your behaviour for a while, and hopefully when the suspension ends your behaviour will have improved.
An account that has been put in this penalty box will have a notice posted on it giving a general reason for the suspension; there is no need to hang out the dirty laundry, the exact reasons are private and only moderators and the affected account need to know.
There are a few things you can infer from that notice though:
'for voting irregularities' usually means the account cheated by creating multiple accounts to vote on their own posts.
'to cool down' indicates the owner was being disruptive, it is hoped that after being away from the Stack Exchange site for a cool-down period that person will see some sense and improve their behaviour.
Initially, suspension periods are short, days or weeks at most. Repeat offenders can be given longer periods. In rare cases, you'll see a suspension date far into the future; that usually means the moderators have given up altogether on that person improving their behaviour. Effectively, that account is asked to not come back, ever.
Because invariably the problems with such account involve a lack of trust or are caused by a fixation with reputation, suspended accounts have their reputation set to 1. The owner thus will no longer have to worry about reputation changes, and the community sees the breach of trust reflected in the reputation score on all posts by that user.