mrtg on my linode just recorded a huge network spike. i've noticed these things in the graphs before and i always thought it must be some anomaly in the data collection. perhaps there really was 100M/s of traffic just now.
I think your MRTG output is probably accurate. I was seeing huge load on the host, now it seems to be down to about 50%. The traffic looks to be all incoming, perhaps a DDOS?