Ballard is just thinking of a variant on the standard rules, although it's a relatively common one. Another similar variant is when tiles are only worth points when they're first laid down, so if you add a G to the word hosts, you only get points for the G. Personally, I don't much care for variants like that, since holding onto common prefixes, suffixes and the letter S is all part of the strategy involved, and as much as it annoys me, it's about the only way games between my brother and I were ever really competitive.