Movies that lack big-name actors and that are shot with shaky, documentary-style camera work don't tend to have huge opening weekends at the box office -- except for in the last two weeks. Following the October record-breaking $50 million debut of 'Jackass 3D' last week comes the similarly astonishing premiere of 'Paranormal Activity 2,' which earned an estimated $41.5 million to open in first place.

The original 'Paranormal Activity' became the most profitable movie of all time last year (made on a budget of $15,000, it grossed $193 million worldwide) through a canny release strategy that involved clever viral marketing and a platform release pattern that built up word of mouth over several weeks as the film expanded across the country. The weekend it opened wide, it took in a healthy $19.6 million. This weekend, however, the sequel used a traditional wide-release pattern (opening on 3,216 screens nationwide all at once), so pundits were predicting an opening in the range of $20 to $30 million.

So why was the opening so much bigger? Credit a strategy that made smart use of midnight screenings, a short running time (allowing more screenings per day), more clever viral marketing (of supposedly "leaked" clips onto the Internet) and very good timing. There were no other wide new releases this week, and not much other horror (save for the weeks-old 'My Soul to Take'), even though Halloween is right around the corner. It'll be interesting to see how 'Paranormal Activity 2' fares next week against 'Saw 3D,' another much-anticipated horror movie that will be the weekend's only wide new release.

Last week's winner, 'Jackass 3D,' slipped to second place and lost more than half of its business this weekend but still pulled in a very strong $21.6 million, according to studio estimates. It's earned $87.1 million so far and will likely top $100 million sometime over the next week.

'Red' also held up well its second week. The action comedy dipped a modest 31 percent, to an estimated $15 million, good for third place. Its 10-day total is $43.5 million.

After opening last weekend on just six screens, the Clint Eastwood-directed afterlife drama 'Hereafter' expanded nationwide this weekend to 2,181 venues. That added an estimated $12.0 million to the $315,000 it earned over the course of the week. That figure was on the high end of the $8-$12 million range pundits had predicted. Apparently, the Eastwood brand and Matt Damon's star power overcame the middling reviews.

Rounding out the top five was 'The Social Network,' down a modest 29 percent to an estimated $7.3 million Over four weeks, the Facebook drama has earned $72.9 million.

The full top 10:
1. 'Paranormal Activity 2,' $41.5 million (3,216 screens), new release
2. 'Jackass 3D,' $21.6 million (3,111), $87.1 million total
3. 'Red,' $15.0 million (3,273), $43.5 million
4. 'Hereafter,' $12.0 million (2,181), $12.3 million
5. 'The Social Network,' $7.3 million (2,921), $72,9 million
6. 'Secretariat,' $6.9 million (3,108), $37.4 million
7. 'Life as We Know It,' $6.2 million (3,019), $37.6 million
8. 'Legend of the Guardians: The Owls of Ga'Hoole,' $3.2 million (2,236), $50.2 million
9. 'The Town,' $2.7 million (1,918), $84.7 million
10. 'Easy A,' $1.8 million (1,632), $54.8 million

•Follow Gary Susman on Twitter @garysusman.