Thoughts on giving away an ebook free on Amazon?

I don't know how many of you know this but you can give your ebooks away on Amazon.com for a limited period to help promote them. There's a top 100 list of free Amazon books which changes frequently and is updated hourly. Most that participate seem to run their programs for a couple of weeks to a month, some longer. Don't ask me how it works from the author side because I don't know. All I do is download them for a rainy day when I have time to read. :) 

The Top 100 Free books are listed on the right. (You can read them on your pc using a free downloadable Amazon app too. You don't need to have a Kindle. i don't.)

http://www.amazon.com/gp/bestsellers/digital-text

Now how they are counted in the Amazon statistics, I'm not sure, and have a question for anybody who's done this or has investigated how it all works. If say for example a thousand readers download your free ebook: does that count towards your sales number even though they didn't pay anything for it? Because even when you get a freebie, the buyer has to go through the shopping cart procedure of adding it to their cart and getting a sales confirmation (for a zero balance) and so on.

I'm curious how many of the high selling Amazon authors took this route and if their sales stats reflect any difference publicly between free and not free.  Say you sell a thousand free copies on Amazon, does that mean you can promote yourself by saying that? I wonder...

If I saw a #1 bestselling Amazon author claim for example, I wouldn't take the time nor know how to check to see if it was on the Top 100 free list they hit the #1 spot. I'd just take it at face value. Because Amazon rotates the list hourly, the odds of you hitting the top spot's very good at some point as it depends on the number of downloads in the last hour, and if yours is a new promo, many people will download it to check it out when they can. I do and have literally hundreds on my computer. 

So technically it's true you are a #1 bestselling Amazon.com book if yours does hit that spot. But would you, my fellow members, consider it ethical to claim that? Answers on a postcard please. :) 

Generally, do you feel it's a good way to promote your book? After all, if you give one of your books away and they like it, they will come back for your other books. But if they don't, you're risking getting a lot of negative reviews posted on the most prominent bookstore online.  

I'm just thinking aloud. Please share your own thoughts about this topic. Thanks!