Graphite/carbon/whisper is a rrd like tool - you give it a number of ticks labelled with a certain metric (facebook.photo.upload) and it counts the incoming ones over a fixed period, averages them, stores the average and goes on and on. Then it draws you a graph over those periods
this is great for "what is normal" and "something has changed over past 5 mins, 5 days, 5 weeks"
some things you want on your dashboard are absolutes that don't vary well with time (cash on hand/ assets vs liabilities)
also the whisper database is awkward to query if you are not aggregating - so you cannot store which customers actually responded to which email campaign - that needs a real RDBMS
So it's really good for watching stuff over time - like you used to use tail -f for. But other stuff needs to be captured robustly and then maybe time graphed
tl dr
Some things are trends - you want to know easily and quickly which ones are going up, and when the trend goes haywire. Use graphite et al.
other things are "action this day" - trend or not you need the email addresses of all users on the blue campaign.
Using UDP you lose a not insignificant number as well
