should a site’s logo always be clickable to go the homepage ?

I think so - for me at least this has become a habit and it's really annoying when I click on it and nothing happens.

I wouldn't say always, but unless you have a good reason not to I think it's a good idea. It's common UI pattern and most people have come to expect that as a way to back to the homepage.

That doesn't mean you shouldn't have other means to go back to the homepage too. As not everybody will think of clicking the logo.

Note to self: make logo clickable. Reason it currently isn't yet, is just laziness.

I mean yes for — agree with Marc in general

Yes, I've clicked the logo numerous times subconsciously and never did what I expected it to do.