Good summary, Oday630.
When setting the starting line, the race committee (RC) will try and give a "fair" start line. If using permanent marks, like buoys, the windward mark is not going to be able to move (obviously), so the starting line has to be tweaked. The line being perpendicular to the wind is the ideal. However, if the windward mark is extremely to one side or the other of that perpendicular line, the PRO (Principal Race Officer) may choose to slant the line slightly towards the mark to make the favored side "less" favored. If one side of the line is heavily favored, too many boats load up there and can cause confusion and interfere with the goal of a "fair" start. In this sense, the position of the mark does come into play both in the setting of the line, and the tactics used. If the RC has done it's job correctly, going fast in clean air is the highest priority. If pin position becomes the highest priority, the RC has not done as good a job as they want.
When the RC is using temporary marks, they can direct the setting of that mark to a perpendicular to the start line. It makes it a lot easier. However, as pointed out earlier, the wind seldom blows from a consistent direction. Most PROs get out to the starting area early to observe conditions, use technology to anticipate wind shifts, and rely on local knowledge to help plan for a proper line. Prior to the start sequence, the committee can change the line position, or the windward mark. Once the sequence starts, however, this cannot be done without a postponement signal. (Postponement is a PRO's best friend!) With multiple starts, it becomes even harder to get a good line. The PRO dosn't want to delay races. Add to that the starts for second (or more) races and as the day goes on, the favored end can become more and more important from a tactical point of view. But still, speed is king. Fighting it out for a favored end while leaving big holes for someone else to blast through ... well, you can see where that can go.
People on race committees are very concerned with running a good race. Starting line, courses, signals, OCS (on course side) calls, accurate timing, boat identification ... wow, the list goes on. Setting a good starting line really matters for a good race, but eithor way, thank the race committee for taking on a really big job.