Anthere: "An interesting comparison would be this one : a french firm already offered to host 3 or 4 of our servers for free. We will cite this firm as a sponsor of Wikimedia on the website. How much does hosting 4 servers per year cost ?"
First I withdraw the 'ridiculously", of course such a nice gesture should be appreciated. My concern was that really large companies would get an almost free ride. Now if we would publish below the logo what the exact nature/amount of the gift is, that would help, as I'm sure e.g. IBM would not want to be listed for $1000. If they wish we could print instead "unspecified but considerable amount", or something like that, at the discretion of the board, who can judge if the proposed gift is a worthy proposition.