“Should a lightning rod have a point?
This was a controversy as early as the 18th century. In the midst of political confrontation between Britain and its American colonies, British scientists maintained that a lightning rod should have a ball on its end. American scientists maintained that there should be a point. As of 2003, the controversy had not been completely resolved.[25] It is difficult to resolve the controversy because proper controlled experiments are nearly impossible in such work; in spite of the work of Moore, et al. [described below] most lightning rods seen on buildings have sharp points. Work performed by Charles B. Moore, et al.[26], in 2000 has helped this issue, finding that moderately rounded or blunt-tipped lightning rods act as marginally better strike receptors. [described below] As a result, round-tipped rods are installed the majority of the time on new systems in the United States. To quote:
Calculations of the relative strengths of the electric fields above similarly exposed sharp and blunt rods show that while the fields are much stronger at the tip of a sharp rod prior to any emissions, they decrease more rapidly with distance. As a result, at a few centimeters above the tip of a 20-mm-diameter blunt rod, the strength of the field is greater than over an otherwise similar, sharper rod of the same height. Since the field strength at the tip of a sharpened rod tends to be limited by the easy formation of ions in the surrounding air, the field strengths over blunt rods can be much stronger than those at distances greater than 1 cm over sharper ones.
The results of this study suggest that moderately blunt metal rods (with tip height to tip radius of curvature ratios of about 680:1) are better lightning strike receptors than sharper rods or very blunt ones.”
http://en.wikipedia.org/wiki/Lightning_rod
and,
Pointing out the advantages of being blunt!
Oct 262009, By Frank Ross
The classic Franklin point design, and the more blunted version of modern lightning rods.
In any lightning protection system, the soldier manning the front line is the air terminal. This simple component is engineered to intercept the downward-moving stepped leader by launching an upward-reaching attachment spark that will serve to close the circuit and direct the flow of current to a solid grounding device, away from a structure and expensive electronics.
Even if you’ve never seen an air terminal in person, more than likely you’ve seen pictures of them on tall buildings, barns, and homes. Most likely the end of the air terminal you’ve seen was very sharply pointed. The theory behind the sharp point design is that it causes the largest electric field and hence is more likely to launch the attachment spark. Sharp pointed air terminals, originally designed by Ben Franklin are a time-honored concept; however, recent research has revealed that blunt rods are slightly more effective in accomplishing this job.
Many modern physicists have shown that, under strong electric fields, the air around sharp rods becomes ionized. This ionized air creates space charges that act to weaken the fields of electricity building up and flowing from ground to components atop roofs, towers and similarly susceptible structures. In both laboratory and field experiments scientists have established that critical field strengths for lightning interception develop more quickly around moderately blunt or blunt lightning rods that those with sharp points.
The most effective air terminal is one with a radius of curvature between 3/16 and 1/2 inch. This is not to say that pointed terminals should be avoided or replaced. They are effective, but moderately blunt or blunt terminals are just more effective.
http://site.electrical-insulators-and-copper-ground-bars.com/blog1/tag/pointed-rods/
Cheers,
Bobbywhy
) the leader from the top of the building failed to connect to the downward leader (ie the lightning rod didn't work in this case 
)
