Not sure why this popped up into the "hot meta topics" today but it did, so I'll throw in my 3¢.
My only concern in lowering the threshold to 3 votes is that there's a tendency to quickly VTC questions from new users - often within just hours of their asking. For some questions, this is perfectly valid, but for the most part, it seems quite reasonable to give someone, especially a new user, 24 hours to come back to edit their question. Often times, there are 3-5 comments asking for more details, pictures, etc. then 5 hours later the question has been closed.
If someone wrote up the question first thing in the morning, then headed off to work, he may not even be able to get back home to see, much less address, the requests for clarification, then when he does, he finds his question already closed and concludes that SE is "not welcoming to new people", bad mouths it, and wanders off someplace else. Remember, not everybody lives & dies by his smortphone, and some people who ask very reasonable questions but just didn't include enough detail aren't allowed access to their phones during the work day.
This is more of a VTC culture issue than it is VTC count issue, but reducing the count to 3 will, I'd think, make it happen more often.
Other than this one issue (and I have no stats to back up
whether how often it actually happens, but there are so very, very few reopen votes in the queue, I'd imagine it does), I'm all for reducing the number of votes necessary.