Возникло беспокойство насчет безопасности передачи этому сайту данных аккаунта Steam:

Комментарии разработчиков на эту тему в ветке на западном цивфанатике:

Цитата Сообщение от species.zero Посмотреть сообщение
We probably need to make this clearer on the website, but the Steam login is completely safe. We're compliant with Steam's third party login policies (found here)

The way it works is, when you click login, you go to steamcommunity.com and give your credentials directly to Steam. If you authenticate successfully, Steam basically communicates back to us saying "this guy's legit," and gives us your user ID. With that ID, we ask Steam for your public info (this is what we get and how we use it). In other words, you give your username and password to Steam directly, and we can never possibly get either.
Цитата Сообщение от m4stermel Посмотреть сообщение
Here's a great post explaining the Steam OpenID system and why it's safe to use with 3rd party sites like ours: http://whatthefrag.net/2011/10/steam-openid-explained/
Если коротко..передача пароля этому сайту миф.
Весь процесс залогинивания, процесс передачи логина и пароля идет на самом Стиме,при помощи официального Steam OpenID созданного для подобных целей.

Здесь небольшое описание механизма на самом сайте стима:
Steam OpenID Provider
Steam can act as an OpenID provider. This allows your application to authenticate a user's SteamID without requiring them to enter their Steam username or password on your site (which would be a violation of the API Terms of Use.) Just download an OpenID library for your language and platform of choice and use http://steamcommunity.com/openid as the provider. The returned Claimed ID will contain the user's 64-bit SteamID. The Claimed ID format is: http://steamcommunity.com/openid/id/<steamid>