Certain corporate needs become so large and fungible that their management is moved to centralized functions and away from the lines of business. IT (along with Real Estate, Legal and Human Resources) falls in this bucket. The result is scale and scope benefits around IT, but LOB's sometimes don't get their needs met. As an LOB, it is sometimes impossible to get the specific IT functionality you need.
For all the talk of whether SaaS will reach some glass ceiling beyond which it won't be a viable alternative for companies of a certain size, I wonder whether companies like Salesforce.com are actually targeting enterprise clients from a different angle: LOB's over IT. The anecdotal stories I hear of LOB's making purchases either with or without implicit IT approval is growing. I don't think companies like Salesforce would ever ignore the IT department, but they can approach LOB's which other Enterprise Software Companies might find difficult.
If you look at IT spend, I would have to imagine that the LOB potential could be significant considering how much money the typical LOB has for special projects. Success would assume they have offerings and pricing attractive to LOB's, but I assume Salesforce is considering this when it builds out its Appexchange.
Salesforce's marketing & sales budget (interesting to note this is how they state it, not in the traditional order - sales and marketing) was close to 55% of revenues for 2005. Seems high and I wonder how much of this was spent on collateral, webinars, etc directed at LOB's.