Here is an interesting real world example that I think not many people know the details about. I don't think any of this information is privileged information. Most of this comes from my (probably faulty) memory with conversations I had with some of Corel's upper management (where I worked). Some of it comes from the public record. There are probably errors since it has been a long time and I didn't not double check the information. It is entirely possible that I was misled right from the beginning anyway, so it might just be fiction. But even if it is, it is entertaining fiction.
In 2000 Microst invested £135 million in Corel. At the time Corel was almost out of cash (if my memory serves they had about $2 million in the bank and with about 1500 employees was going to run into a problem with payroll sooner rather than later). Corel issued new stock to cover the deal and I think it represented about 25% of total equity. This stock was non-voting, but came with a veto over new acquisitions. The rationale was that since Microsoft and Corel were playing in the same office productivity software market, Corel didn't want them to be able to dictate what they were doing, but at the same time Microsoft wanted to protect their investment against acquisitions that they thought were poor judgement.
At that time, growing your business through acquisitions was all the rage and the Corel management team (led by it's relatively inexperienced CEO at the time) was quite keen to use some of the new capital to grow their business. Microsoft encouraged them and even brokered meetings, etc, etc. In the end Corel set up several acquisitions, which of course took some time to go through all the approval processes.
In around 2003 Microsoft sold their Corel stock to the venture capital firm Vector for about £13 million (10% of their original investment). It is possibly not a coincidence that this is a venture capital firm that Paul Allen was involved with, but who knows? According to what the then Corel CEO told me at the time, Vector then threatened to use their acquisition veto if the board did not agree to back a complete buyout by Vector. The problem was that the penalty clauses for backing out of the acquisitions would once again put Corel into a very difficult situation financially. Feeling like they had no choice in the matter, the board approved the buy out and recommended that the investors accept the deal.
Vector bought up all the remaining stock for $133 million, using about $80 million of Corel's remaining cash to finance the deal. Very soon afterwards they laid off a very large number of employees (including me ;-) ) and concentrated on profitability. As far as I know, Vector have managed the company exceptionally well since then.
I heard from trusted sources that Corel's CEO at the time gave up a multi-million dollar parachute to accept a job at Microsoft, so I suspected that there was never really any need to feel particularly sorry for him. But you can see that one seemingly innocuous condition from an investor who is saving your butt can lead to the most unimaginable outcomes.