got mine on the 26th in the morning within several hours of being available on newegg and it sold out by the end of that afternoon. it was a good find too, because this was before the actual release date, and it wasn't actually advertised anyway exclusively on the sites front page. you had to go to the tablet section and even then it wasn't visible until you looked in the 'new' category. it just wasn't prominent at all. luckily I was browsing the site every day looking for price changes on other tablets. got a super deal with premium quality $60 over-ear headset for free as a bonus. I was already in the market for a good headset, so as far as I'm concerned I only payed $170 for my 16GB N7.
google expects to sell around 12 million units over a years period, which comes up to about 33K sold per day. I expect they'll meet or surpass those expectations.
I however think that a lot of companies just don't know how much stock they'll need this early on and don't want to overstock. the new nexus 7 should bring aboard alot of new tablet owners, which also makes it hard to judge how much stock is needed.