Samsung Austin Semiconductor used to have an "eat lunch with the president" program where groups of four or five from each department would each lunch with the president at least once a year. Obviously nowhere near as immersive as this program, but still having the opportunity to ask several off-the-cuff questions like, "Why did Samsung choose Austin?" definitely added value for me.
From my perspective, the real value of the lunches was strictly building rapport across the company. At some places high level employees (doesn't necessarily have to be management) often feel unapproachable and they feel more abstract concepts than people. Having lunch with them re-enforces they are also people, people you may even get along with.
Other companies I've been at only do Q&A sessions with large groups of employees, and this is still useful, but the format doesn't help the culture. The answers you get are often the company line, and you cannot dig deeper. The people answering the questions are still abstract identities that appear to tout that company line, with no real personality.
However, being a TA also involves active advising and commenting first on document reviews (a lot of executive communication at Amazon is via written documents and review meetings that begin with a doc read). Many of our executives were former TA's.