Flags - the really big RED ones

What is the deal with this 'known extremist' who is allowed to board an international flight to the US to then proceed to almost be successful in blowing it up? Remind me later to go over the question the pundants were asking about why blow up the plane during landing and not over the ocean. That one makes me just as crazy.
OK, now I am not in the business of gathering, monitoring, analyzing, and interpreting intelligence information so please don't think that as I write I am doing so with any authority on the subject. It does seem to me that logic, a common mental process that many people utilize, is the first skill set you would work with make when dealing with intelligence gathering.
All of this after the fact information about the many dots that were out in the intelligence world that didn't get connected really didn't make any difference ahead of time. Is it a problem? Sure it is and having 16 agencies gathering intelligence doesn't make sense either, but that is another blog.
If someone who was at the ticket counter or whatever had common sense, (and used it) when they have someone buying a one-way ticket, paying in cash, bringing no luggage other than a carry on, and doesn't have a coat on during the dead of winter at his destination...I don't know how many of those really big RED flags should there be to make someone think twice or maybe three times? Hey, if they are afraid to make a decision then call someone over to help with that decision.
Oh and the deal about the pundants asking why blow up the plane during landing and not over the ocean. Really? Are they serious? That can't be something they just don't have a clue about. Hello??? More people will be killed, the airport would be closed, all other flights in the country would be effected, they would terrorize more people, need I go on? It is really simple don't you think, when you really think, hard and serious? Come on...give me any good reason why we can't use our common sense more often?