Our code of conduct has a rule that has been around since the inception of FBTB:
One account per person: Creating multiple accounts, for any reason, is grounds for an immediate ban. If you have any problems logging into your account, contact the staff.
There are a lot of reasons for this rule, most which are probably obvious. We don't need someone pretending to be someone else, we don't want someone rigging the votes in contests, and we don't want multiple entries from the same person in drawings or contests. And that's just the obvious stuff related to contests.
However, in the past few contests, we've started to see more and more of multiple people coming from the same household registering for a contests (some brothers, fathers/sons, mothers/daughters, etc.). While we don't discourage different people having their own accounts (in fact, we encourage it... sharing accounts just leads to messy situations eventually), we have to make sure that all of our contests are fair to everyone. The best bet, if you're doing something like this, is to disclose it first. If you don't want to post that relationship to the world, feel free to contact any member of the staff to explain that you have more than one account.
Going forward, some contests, like our annual MOC Madness or any contest that has a limited number of entries, will be restricted to "one entry per household." We promise to be clear in the rules for the contests going forward to avoid confusion, and even remember... just because you can only have one entry that doesn't mean you can't build together and share ideas. The best thing about LEGO is when you build with someone else, and sharing your ideas.
If a contest doesn't put a restriction on one-per-household, different accounts can still enter, but remember, there are still restrictions for who can sign up for the site (such as the age restrictions). There's also some basic expectations in how those entries come up. Pictures shouldn't be identical, neither should the writing or posts. People are different, and that should be apparent when we view the posts.
As most of the staff are parents, we understand wanting to help our kids get the best stuff they can out there, but everyone who enters a contest needs to write their own stuff and take their own pictures. When the staff sees two posts from different people that are almost identical, be it writing style, pictures, we're going to assume that someone is trying to sneak in two accounts. We'd like to err on the side of allowing it, but there are just too many instances where that's not the case. As we said above, your best bet is to be up-front with us before we bring out the ban hammer and it moves to some awkward emails.
If the above post didn't offend you, you're probably reading it wrong.