At Citrix Synergy 2011 in San Francisco last month Simon Crosby made the case that the biggest barrier to the adoption of service-provider offered cloud services is the understandable lack of trust on the part of enterprise customers. Well it looks as if he and fellow Xen luminary Ian Pratt have decided to do something about that lack of trust and are moving on from Citrix to address the problem at its source. Ian and Simon announced today that they are both leaving Citrix and taking key roles along with with Gaurav Banga (the creator of Phoenix Hyperspace) as co-founders of cloud security start-up Bromium.