At LinkedIn, Roger Slade has a (non-exhaustive) list:
1. Working for a Competitor.
2. Overcompensating themselves.
3. Not Devoting Full Time and Effort to the Business.
4. Failure to Disclose Important Facts.
5. Binding the Business to Agreements that Are not Approved or Otherwise Disadvantageous.
6. Duty to Inform Partners of Material Facts.
7. Failing to Make Required Distributions.
8. Denying the Shareholder Opportunity to Participate in Management.
9. Using Corporate Funds to Pay Personal Expenses.
10. Freezing a Minority Partner Out of the Business.
The full piece, which describes warning signs and what to do to protect against such actions, can be found at LinkedIn (membership required).