I checked in late at the Embassy Suites Baltimore Inner Harbor. It was 11PM or later when I needed to use the Internet for work. I was given the password to login but never use those since I have a login for any Hilton property.

No matter what I did, I couldn't get the Internet to connect or give me the standard Hilton login page. I finally gave up and used my smartphone as a hotspot to get my work done. The next morning, in the elevator to breakfast, I was talking to another Diamond member and he commented that he had the same issue and had to call the front desk and provide the MAC address of the the device he wanted to connect. I was shocked in hearing this since each individual device has its own specific MAC address and can be tracked back to the owner.

It explains why I couldn't connect. Is this property aware of the cyber crime implications of them asking for this information? If these addresses are stolen and someone clones that address, which is very easy, the owner would be liable for any malicious behavior done by the cloned device. Is the Embassy Suites and Hilton willing to take on this liability?

I have informed the Diamond desk of this practice at this property. I would avoid staying at this Embassy suites until this policy is removed.

No it does not explain why you can't connect. The reason you can't connect will usually be because of one of several (known reasons) when you access the non secured wifi (no password needed for that) , you are effectively signed in to an 'intranet' local loop, with no access to the global internet. Now as soon as you open a browser (mozilla, crome etc etc) you should end up at the hotels wifi internet access signon page. If the page is not presented, your laptop can not be registered and connected through the intranet and out to the world wide web internet.
(Also If you know the URL of hotels initial logon page, you can simply type that into your browser url line, refresh and login. )

Your PC/Laptop will actually have 2x MAC addresses, one for each of a)wi-fi b)Cable/LAN/ethernet connection

Your mac address accompanies all your inet traffic, and unless using an encrypted wifi is visable to everyone. Even if https:// ssl conections, whilst others can not eavesdrop on your browsing, each site you are connecting to can, and everytime you use a site or buy something etc on internet, companies can record your MAC address (not IP ) for security purposes.

MAC addresses will not be cloned, like your mobile phones SIM card or phones ID. It is not quite the same thing. In fact when you connect to any site on the internet, your MAC address is broadcast/visable to that web site whether your access is http:// or ssl secured https://
(So every hotel you connect to, cable+wifi automatically has your MAC address info )

What your friend in the lift was trying to explain is that the hotels IT Specialist, who controls the access to the hotels wi-fi, can help by allowing you to bypass the hotel wifi logoin page .. By adding your mac address to the hotels server.
Once added the hotel wifi charging logon page will be bypassed and connect your "Known Registered Laptop" everytime until IT support at hotel removes your mac address info.

Sites that you pay/subscribe to will monitor the mac address of subscribers connected Laptops/Pc's to ensure the logon credentials are not being shared to save paying for a service. I am happy with this, as if the service uses IP addresses to prevent sharing of logon-ids, outside of your home, every inet logon will have a different IP address quickly leading to one being blocked.

These statements are entirely false unless you have a direct connection to that website (i.e. are on the same intranet as it). As soon as your traffic hits a router, your individual computer MAC address is wiped from the packet and that router's address is inserted.