I've experienced my share of light chop to mod chop, but, I actually experienced Mod-Sev once on a dash-8 from YYC-YEG in January of this year. It's a short hop (45 mins) and about 8 people got sick on the plane. It was the worst and longest 45 mins of my life and the only time I've actually be terrified on a plane. All I remember was the smell of vomit and constant thrashing around inside the plane.. It was very relieving when we landed that's for sure... Everyone was pale as they got off..

My cousin was also flying from YVR-YEG the same evening on a different airline (737) and they had to have an ambulance meet their plane as they had some injured pax.