I think that there is a misunderstanding in the marketplace, a perception by Software as a Service (SAAS) prospects and customers, that the only way they can have a solution that is available from "anywhere" is if they choose a cloud solution. This is a ridiculous assumption and one that cloud vendors seem to be capitalizing on. World Wide Web accessibility should not be considered a discriminator for on-premises versus cloud debate, and it certainly shouldn't be considered an advantage for an SAAS solution option. If anything, level of flexibility in accessibility should be considered a disadvantage to SAAS offerings, since SAAS offerings by definition, require some form of WAN or Internet connection.
For on-premises deployments of Web-based software products, accessibility from the World Wide Web is a matter of corporate policy and network configuration. In many highly secure environments governed by extensive policies, procedures, and directives; it may seem "impossible" for a business group to receive permission to have their Web portal published externally, to the World Wide Web. This is not a technical matter. This is a policy matter. In that regard, SAAS does make the "impossible" possible, by allowing business groups to bypass rules that they would otherwise need to follow if they went the on-premises route. So, is enabling a customer to circumvent a procedure truly a competive technical advantage to SAAS? I don't think so, and I don't think marketing should communicate it as such.
I think an underlying problem that this situation highlights is that many businesses still lack the ability to effectively prioritize their Information Technology initiatives and align those initiatives with the demands of the business. It is easier and more beneficial/less costly for a business unit to go rogue with an SAAS solution than it is for them to work with IT. This situation also points to a flawed management practice of allowing business units to dictate their own technology solutions as opposed to following a single Enterprise Architecture strategy. Whatever the case, "accessible from the Web" isn't a technology discriminator for SAAS, and vendors shouldn't confuse people into believing that it is.
References
LeClaire, J. (March, 2012). Should CRM Apps Be in the Cloud? Retrieved March 12, 2012 from
http://www.crm-daily.com/story.xhtml?story_id=030001S1KJNI&nl=1&full_skip=1.