Salesforce.com has had a lot of outages, but it seems like customers have not been particularly upset by them. How important a factor is reliable connectivity when evaluating on-demand options? Do we really need to consider a service level agreement (SLA)? What other factors are important to consider at this point?
Simply put, yes. Reliable connectivity is paramount to any solution you implement. It makes no sense to invest in CRM systems and not be able to depend on them to get the job done on a sustainable basis.
In the IT world, the battle for four or five "9's" (99.999% uptime) of reliability is an age-old battle, but as a customer, you should demand the highest reliability factor possible, for the best price possible. 99.99% uptime (not including scheduled downtime and maintenance windows) is achievable. SLA's should be built into the service contract you have with the provider -- this is an industry standard practice.