Given that the IBM logo disappeared from our website, I suspect that IBM no longer sponsors us. Meanwhile, CrossValidated is now sponsored by AWS (machine learning). Are we still sponsored by IBM? If not, why not? Anyway, this sponsorship does not seem to have been beneficial to us. We need a more effective way of attracting experts.
Quoting this comment by Stack Exchange's Director of New Community Development, Robert Cartaino:
The IBM sponsorship has concluded, but AWS has signed on to take over later this year! We are currently finalizing the materials needed and it should go live when everything is completed.
According to the Wayback Machine, the logo started to show somewhere between January 10th and 14th.