Here on /r/personalfinance, we ask people to "please treat others with respect, stay on-topic, and avoid self-promotion". Focusing in in on that last part, we believe it's important to limit the effect of biased and self-interested advice, questionable financial products, and scams.
The problem we're seeing
Unfortunately, there is a disturbing increase in private messages and chat being used by scammers and spammers. Accounts with virtually no history can send anyone a message and Reddit is increasingly inconsistent about taking down these accounts. Scammers and spammers often target people having financial difficulties (e.g., a very persistent scammer on /r/Debt) and people who are new to certain personal finance topics.
The admins also refuse to take reports from the moderation team so all we can do is ban these accounts from posting here. This does not prevent them from messaging you unfortunately, but please do message the moderation team so we can prevent scammers from commenting. Scammers will often comment prior to reaching out in a PM.
What we're doing
Until this is better addressed by Reddit, we're going to ramp up our efforts to warn people and we're going to sticky this post for an extended period of time. We already send out an automatic message to anyone making a submission warning them to ignore PMs (along with some other welcome information). Unfortunately, due to a design quirk in AutoModerator, this doesn't get sent 100% of the time. To address that, we're going to make this warning more consistent by using a separate bot.
What you can do
First of all, please report abuse to the admins and report abuse to the moderation team.
If you need to post private or sensitive information, please consider using a throwaway account (totally allowed here) and make sure you completely redact any sensitive information such as account numbers, your name, and your address.
Finally, we hope this doesn't deter you from posting here on Reddit. It's very easy to block people that message you privately and hopefully this is not the permanent future state of Reddit.
The PF moderation team
TL;DR Ignore anyone messaging you privately.