I have been observing a trend where business users or information workers become more-informed and educated about the range of productivity software options available in the marketplace and start using them without any help or consent from IT. If taken as a threat IT could potentially attempt to block these applications and users get frustrated and still find a way to work around these restrictions and if taken as an opportunity IT takes the hint and standardizes these options across the organization to speed up the adoption. The later is a win-win situation; IT has beta users doing acceptance testing for them without being asked and IT can focus on more strategic tasks, empower users, and support users' aspirations and goals by providing them with the tools that they need. This trend follows the rule of the wisdom of crowd. If software is good enough it will bubble up. Firefox is a good example of such a trend. The users started using it way before IT decided to include it in the standard machines that they give out to the users.
I can understand why the enterprise applications such as ERP and SCM are not likely candidates for bottom-up adoption since they require upfront heavy customization and are tightly integrated with the organization’s business processes and has complex requirements such as compliance, process integration, workflow, access control etc. requiring IT's involvement. This is slowly changing as SaaS becomes more popular and the applications can reach to users directly and provide all the benefits to overcome the adoption barriers by eliminating the upfront IT involvement. Zoho People is a good example of such an application. Salesforce.com has achieved bottom-up departmental adoption despite of IT’s traditional claim to CRM ownership. Departmental solutions do have drawbacks of becoming silos and make intra-department integration difficult and that could result into bad data quality of due to redundancy and lack of effective collaboration. To overcome some of these concerns collaboration is a key feature in an application that is a likely candidate for bottom-up software adoption. Google Apps is a good example where they introduced a feature that allows users to discover each other and potentially collaborate with across departments in an organization.
The decision-making is tipping towards the information workers and many business users don't necessarily see the needs of some pre-installed on-premise solutions. The cultural shift to embed their personal life with the professional life is also making certain web-based tools their choice. If I am a vendor that finds a CIO sale a bit tricky, I would be very closely watching this trend.