Google have a policy to let their staff build anything they want one day a week.
Gmail was the result of one staff members output as is google calendar !
Though presumably these are not 1 man day a week operations now. Gmail through the iphone is great too.
Though Facebook are now stealing (brain draining) google's staff.
Don't think gmail is still beta. I remember when it was a proper beta and you had to be invited to use it and at the time it had 1GB of storage which was huge as Hotmai/Yahoo only had like 100MB. Took me ages to get an invite! Heck I remember when I joined yahoo mail and I had 15MB of email storage
warranty.. if its a full blown 1.0 release, it makes them liable whereas if it is classed a beta product, you accept it warts and all and it therefore removes the liability if something goes wrong