Multiple.. means more than one ..like two ..or seven ..or 5 ..or 13 or 27 ..all of which are considerably less than 50..
Many here run multiple sites ..have done so for years ..have had no problems ..neither before nor during Panda runs..and will continue to have no problems just because they have multiple sites..
Beware of inaccurately extrapolating misunderstood commentary molehills into mountains of FUD..
Having "multiple sites" ( and all in different "niches" ) means you're safer from Panda or "whatever" ..because if one is hit ..you have the others ..providing you didn't interlink them to death and use all the same templates etc..if you did ( dumb !) then if one falls it will drag the others down to a greater or lesser degree..