Create one scroll view that you can drag on both X and Y. Create columns of tweets under your scroll view like so:
Scroll View (and UICenterOnChild, and UIGrid if you like)
- Column 1 (UITable to make positioning easy, or do your own logic)
-- Tweet 1
-- Tweet 2
-- Tweet 3
- Column 2 (UITable)
-- Tweet 1
-- Tweet 2
-- Tweet 3
The trick is to use UICenterOnChild (or a similar script of your own design) to snap to columns, while retaining the ability to scroll vertically freely.