One thing I have seen (with varying degrees of success) are event aggregators that attempt to do root cause analysis and suppress downstream events.
e.g. if you lose a hub WAN link and are thus unable to reach 10 sites over that connection, you don't really want to receive the notifications that the WAN is down and 10 sites are also apparently down; better to receive a single notification saying that the WAN is down, and this is affecting reachability to 10 sites. Similar capabilities were tied in to the NOC systems so that when a particular element failed, the NOC would know which customers were impacted, and thus could proactively notify them of the issue.
There are a number of approaches to automated root cause out there, and it can be complex, but if you can get it right and tie it into other data sources to pull added intelligence for your alerts, you can make great steps towards minimizing the number of alerts hitting the users who get notified.
