Intel gathering happens all the time. Corp dev people go on lots of fishing expeditions under the ostensible guise of acquisition talks. Sometimes they don't even need to mention an acquisition; they know that most startups will hear "BigCo wants to talk to you," and will leap at the chance to take the meeting. Bingo bango, they get free market intelligence, and all it cost them was a few hours of their time.

Things get messier when you talk about intentionally "derailing" companies. I'm sure this has happened before, but this is legally murky water. BigCo doesn't want to be perceived as anticompetitive, or as acting in bad faith. (Of course, it's very hard to show that they are acting in bad faith. Keep that in mind if you smell anything fishy.)