One example: I used to work for a company offering a security-related product with crippling, fundamental security problems. The flaws covered everything from improper use of cryptography to failure to validate external input, lack of proper authorization handling, and even "features" fundamentally at odds with any widely expected definition of security.

This company continues to survive, and has several large clients. But the liabilities of the current code base are massive. Worse is that the clients aren't aware of the deep technical problems, nor is there any easy way for then to be. In a very real sense, this company is making some money in the short term (I don't believe they are profitable yet) by risking their clients' valuable data.

In general, the concern by the grandparent is that there are projects out there that are producing some revenue, but are essentially zombies. Every incremental feature adds more and more cost, but there's no cost-effective way to remove sprawling complexity. The project will die, taking along with it significant investor money.