The last two seasons, Joe Johnson's FT Rate* was 21.1. In 2008-09, the league average was 23.6. In 2007-08, the league average was 23.1. Getting to the foul line has never been a strength of Johnson's game. In fact, I contend it's what separates him from similar, but more effective, players.
*(Free throws made * 100) / Field goal attempts
The league average has dropped a hair so far this season (23.0) but Johnson's free throw rate has plummeted. His season average was last at 21.1 or better after the 13th game (the home win over Houston). It currently sits at 15.9.
Using the sortable league leaders at Knickerblogger.net, one can see that Johnson is 19th* in the league in points per 36 minutes. Of those 19, he's also 19th in FT Rate. Not necessarily damaging in and of itself. Those guys above him score more often and they get the line more often. They get to the line much more often. Monta Ellis ranks 18th (of the top 19 scorers) with a FT Rate of 22.1. Eleven of the 18 players ranking ahead of Johnson in points per 36 minutes sport a FT Rate more than twice Johnson's rate.
Of the top 50 scorers (per 36 minutes), from Carmelo Anthony all the way down to Manu Ginobili, Joe Johnson ranks 47th in FT Rate. Only JR Smith, Charlie Villanueva, and Jason Richardson trail him.
*He's listed 20th but I'm excluding Kevin Martin who ranks 4th but has only played five games.
What does this mean? It means that Johnson deserves credit for being a great shot-maker. No one else in the league scores at his rate with anything approaching so little production from the free throw line. It also means that Johnson can't be consistently efficient. He shoots well from the free throw line (82.7% this season, 79.1% for his career) but doesn't get there often enough to take advantage of that high percentage as a consistent foundation of his offensive game. Instead, he must string together made field goal attempts to score efficiently and they're (obviously) much less likely to go in than are free throws. Johnson's making 48.4% of his two-point attempts this season (46.7% for his career) and 37.5% of his three-point attempts this season (37.4% for his career). When he's hot, and he's ticking off points two or three at a time, he's more than capable of carrying the Hawks offensively. When he's not hot, the occasional single point would come in handy to break up the strings of zeros.