Minor Description
MarkupContainer.add has O(n^2) complexity on the number of childs, because it searches through all other childs for a child with the same id. This may not be much of a problem in most situations, but in large tables, the performance can get very bad.
Constructing a table with n rows, with 6 cells in each row takes (10k iterations) in Wicket 6.20.0 (Wicket 7 should be comparable, but WICKET-5981 kills perfomance badly):
10 -> 132ms
20 -> 245ms
40 -> 465ms
80 -> 1000ms
160 -> 2444ms
320 -> 6989ms
640 -> 23201ms
1280 -> 80784ms