Looks like someone pushed the wrong SSL cert to production:
www.bing.com uses an invalid security certificate.
The certificate is only valid for the following names:
a248.e.akamai.net , *.akamaihd.net , *.akamaihd-staging.net
(Error code: ssl_error_bad_cert_domain)
Australian Ebay (https://www.ebay.com.au/) has had the same problem for months, although I appear to get no response for https://www.ebay.com, so I'm not sure what their policy is on SSL access to the homepage.
I expect that Microsoft will fix Bing much more quickly.
The post does not explain why Akamai's cert is being used. If bing over SSL were working correctly in the past---which I believe to be true---and given that Bing were using Akamai in the past, why the problem now?
Bing doesn't do SSL and never has at that domain (they previously used ssl.bing.com). you're seeing an Akamai cert because Akamai servers are hosting bing.com.