Critical Hit (of Information)

Over at Professor Pope's blog, I came across the question of DM expectations vs player decisions, specifically as it relates to the direction of the campaign.  In a past game, he dropped some hints to the players, expecting them to take the bait and run with it.  Instead they went a different direction.  I'm sure this has happened to many fellow DMs, myself included.  In the past, I may have scrambled to make something up and tried to force the players to link back up with my designed direction.  Railroading? Oh ya.  More recently, I have come up with another alternative, loosely defined as follows:

1. If the players need a key piece of info, make sure that they have several ways to discover it.  If said piece of information is so critical to the forward momentum of the game, they MUST find it.  In this situation, I usually let the players find tidbits of the info with almost every type of Skill they have.  Even a low skill check result will get them a crumb to follow.  
2. If you drop plot seeds and adventure options to the players, who then fail to follow said devices, then be prepared to have the seeds escalate.  In my current game, the players have a to-do list that is a mile long.  Professor Pope's (former) character was recently informed that his home town had been overrun by undead and that some family members were missing.  As a group, they decided that their current mission was more important and put the undead-city on the back burner.  It has been almost a year in game time since that first message came to them.  If they were to investigate it now, I'm sure that the situation has changed.  Maybe another group of heroes has cleansed the city?  Maybe the undead in the city have expanded?  Who knows?  My point is that the DM should be prepared to let loose plot threads unravel and escalate on their own.  And the occasional thread should come back to haunt the players.  But it is critical that only a few of these circle back on the PCs.  If every loose plot thread screws with the group, the players will get frustrated with their failure to complete these items.  
3. If the players need to meet an important PC or have a certain encounter, yet they go in a different direction, be prepared to improvise and have the interaction occur elsewhere.  This is often called Schroedinger's XYZ (Dungeon, Gun, etc).  The players don't know what is around the next corner until they come across it.  Use this uncertainty to place your encounters as needed. Just because you write an adventure to happen a certain way, you must be prepared to change it if required.  Don't lock encounters to specific sites.  Instead, loosely tie encounters to general locations and have the PCs encounter them in a natural, organic manner.  
4. Don't waste time writing up the backstory to every NPC, city, nation, etc.  Unless the PCs will learn the information and it is relevant to the campaign, ditch the details.  A DMs job is already hard enough without having to put every detail down in writing.  Be prepared to wing it by having a list of vague details handy.  Don't go into the history of the blacksmith in Town A unless he will be encountered again and again.  Any information that you write that is not shared with the players is just a waste of your time.  So, either share it with them, or skip it altogether.