I noticed LibreOffice runs reasonally well on Raspbian now, so this got me thinking of the following scenario.
Suppose a small business decided to use 10 to 20 Raspberry Pis in its office as primary productivity machines. All have Raspbian with LibreOffice installed, along with Midori, Abiword, GIMP, and other useful software, however most required usage is lightweight. Since Wi-Fi is required for an office connection, each Pi would be fitted with a powered USB hub and USB Wi-Fi adapter, and connected to a conventional office PC monitor (LCD with DVI), SD card, keyboard and mouse.
First of all, in terms of equipment cost, space and power consumption, this could save a lot of money over conventional PCs if the requirements are lightweight enough. Perhaps in a third world scenario, it could work.
The downside, however, is the loss of productivity from the relatively weak Raspberry Pi's performance, in comparison to using more powerful desktop PCs. Perhaps a mixture of Pi's and more powerful PCs would be needed in practice in such an office scenario.
As software improves, however, this does seem more feasible. We already have the ARM HF leveraged, safe overclocking, and LibreOffice performing well enough, as well as 512MB RAM models. When we have hardware-accelerated X drivers, performance in productivity applications may be given enough of a boost to be a real alternative for lightweight business use.