Citigroup (NYSE: C) shareholders are not waiting for the next shoe to drop. According to the Wall Street Journal, they filed a lawsuit today in federal court [subscription required] in Manhattan alleging "Citigroup executives recklessly purchased subprime loans to be used for future collateralized debt obligations and then made allegedly improper statements regarding the financial services company's exposure to the subprime market meltdown." The suit also alleges that some defendants sold shares while in possession of "material nonpublic information" about the company's exposure, securing more than $36 million in proceeds.

Citigroup and former chief executive Charles Prince are named defendants, as well as other top executives and directors, according to the Journal.

This is the second suit filed this week. Earlier in the week, participants and beneficiaries of Citigroup's retirement plans filed a suit related to Citigroup's derivative trading, alleging the company's stock was an "imprudent investment" for the plans because of "mismanagement and improper business practices at the company," the Journal wrote.

Investor lawsuits must climb over a very high bar to be successful, but Enron investors did have some success. For the sake of Citigroup shareholders I hope they too can recoup some of their losses.

Lita Epstein has written more than 20 books including "Trading for Dummies" and "Reading Financial Reports for Dummies."