There seems to be a huge number of very low-rep users called "guest." Is this the same individual, or a small number of individuals, who are using "guest" as a burner account? Does this violate either the terms or community norms of ASE?
All the information I give here is generally available and does not come from my moderator privileges.
First of all some general information on this:
Having multiple accounts is okay, as long as they do not do something that cannot be done with a single account, which includes almost all interactions of the accounts: How should sockpuppets be handled on Stack Exchange?
The default avatar of any account is an identicon based on a hash of your IP or, if provided, your e-mail address. It is extremely unlikely that two identicons coincide by chance. See: How is the default user avatar generated?
Moderators have further tools to tell if two accounts belong to the same person.
Now, some observations and conclusions on the accounts in question:
They have the same avatar, so they very likely come from the same IP or provided the same e-mail address. The alternative is that they use the identicon image as a manual avatar (like I use a picture of a glass head), but then again, they intend to be identified with each other.
They are unregistered, which makes the most common forms of sockpuppet abuse (in particular voting) unavailable to them. If such accounts commit sockpuppet abuse, it is usually by circumventing rate limits, question or answer bans, or suspensions. If you see any indication for this (or some other kind of sockpuppet abuse), please flag for moderator attention.
Only mods know if two accounts belong to the same user and we obviously cannot say anything. So without commenting on this particular user, a single user having multiple accounts is sometimes fine, but sometimes a flagrant violation. You cannot have two accounts to up vote your own content or artificially increase your reputation. If you are suspended you cannot create a new account to circumvent the punishment.
Some people create new accounts to ask (or answer) something anonymously. That is a valid use, as long as your accounts never interact. Some really high rep users want to be able to do things as a lower rep user and that is okay, more or less.
The most common case of multiple accounts is people either losing their login info or not understanding the system. If your see this, you can leave them a comment about how to merge accounts (contact us link at the bottom of every page) or flag it. (In this particular case, we are aware of the multiple accounts so please do not raise a ton of flags.)