There seems to be a particular strategy that is "en vogue" for this classic RISK map. A number of players have recently been dominating by keeping all of their forces consolidated into one territory. Continent ownership is not necessarily a must to win with this style, as long as it's 4+ players.
Pros? Cons? Bueller?
It can be a bit dangerous though too by putting all your eggs in one basket.
"But many who are first will be last, and many who are last will be first." Matthew 19:30 - Good strategy for life and WarGear!
I see this among my friends in lots of games. Especially once cards get high enough, that no one really cares about continent bonuses. Everyone is trying to get a card, and by putting all your units in a few # of territories, no one will want to get a card from you because they have to take so many more units for that card.