Some people are referred to as being “so smart they never stop thinking so they’re hard to follow.” That’s not smart, that’s stupid. If you are expected to impart information to another, you must be smart enough to deal with your audience.
There’s a guy yapping about FTP’ing files and ATM LANs and such, when he really doesn’t need to show off how much he knows by spouting acronyms to a non-technical audience.
One of my bosses was mentioned as being too smart a while back. The catalyst was his penchant for changing his mind on major philosophical approaches for documents or test programs. The truly intelligent don’t need to show off their knowledge, and they are capable of forming an opinion or decision before telling it to others. If you can’t get your thoughts in order, you’re not intelligent, you’re scatterbrained. One need not be smart to confuse others. To enlighten others without seeming effort is a good hallmark of intelligence, though, in my opinion.