It may be a common thing individual developers that play with everything do. I doubt it's common for businesses to deploy production apps across multiple clouds. Unfortunately I don't think that survey will be able to answer that either way.
I've been running that survey for a little while, with a non-HN audience. More than 50% use more than one provider, and people managing more than 10 servers (who I presume are doing it for a business) don't seem any less likely.
(Thanks for all the answers BTW. I especially liked the OrionVM vs Ninefold comparison someone did in a comment - I'm from Australia, and for various reasons are reasonably familiar with the offering available. Alex from OrionVM is on HN, too)
