I’m as tired of the ‘cloud’ word as the next guy. But cloud is everywhere at the RSA Conference in San Francisco. And here’s an interesting twist: The folks at Zscaler, a cloud security start-up, made their case to me that cloud-centric security is pressuring traditional on-premise security appliances. Is that a fact or a marketing claim?

As Zscaler CEO Jay Chaudhry spoke with me, he made the case that managed security service providers will need to shift away from appliance-centric architectures to cloud architectures. The reason: It’s impossible to predict where mobile employees will be working on any given day, so it’s wiser for them to leverage cloud-centric security (running in distributed data centers across the globe) rather than appliances at fixed office locations.

I’ve known Chaudhry for about three years, and he’s a veteran of multiple start-ups and technology waves — so I tend to listen when he speaks. Zscaler, by the way, has set up a SaaS-centric partner program that delivers recurring revenue to MSPs and VARs.

But back to the topic at hand: Are cloud services pressuring on-premise, purpose-build appliances? I realize quite a few companies have made the switch from appliances to SaaS. One example involves Dell shifting its Managed Services platform (the acquired Silverback offerings) from appliances to SaaS.

But on the other hand, I keep hearing from a range of on-premise security hardware providers that are now integrating with a range of online backup, disaster recovery and SaaS security services.

Like everything else in IT, I think this is a case of lines blurring. Zscaler is generating some buzz and has signed up some companies that have as many as 300,000 users. But I think security appliances will stick around for quite some time.