As someone who works at a Bitcoin/Ethereum company, and has passionately followed Bitcoin since 2011, every time I hear "blockchain" as a proper noun a piece of me dies inside. It's like saying "This Is Your Company on Website."
Shit! Where's my checkbook?! I have to cut these guys a seed round before they try to actually build anything.
Otherwise it'll become apparent that this series of words have nothing to do with each other!
These days the blockchain world revolves around large companies(or groups of companies) setting things up for internal consumption and consulting companies trying to get in on the action to help those large companies with the setup.
I think the crucial distinction is whether you're pointing at an approach versus some specific implementation. 'Blockchain', as I understand it, is a particular approach that isn't linked to some particular instance.
"Your company on website" doesn't work because there's really only one 'web'. "Your company on Facebook" does work, as does "Your company on SCRUM/NoSQL/AOL/Mobile/etc."
I'd prefer "on a blockchain", personally, but "on blockchain" doesn't strike me as too egregious.
And what about making it more specific, as in: "This is your company on blockchain technology"?