If you check the poll results that accompany the main thread on getting people to push the NHTSA to get Yamaha to do what they should you will see that there really seems to be no correlation except one related to age - and even then . . . without population figures for the entire of what's out there getting an idea of what the statistical distribution and thus the trigger factors is a difficult, if not impossible task.
The probability is that in general the older the macine the more likely it is to suffer the proble - and it is also likely tied to operating times and operating environment - humid weather encourages corrosion; Hot weather allows heat to collect and time exacerbates all problems.
You have two choices; You can do nothing and wait for the bike to fail or for there to be a recall or you can invest in a bypass harness and probably avoid having to go through the issue and then get Yamaha's fix if and when they provide it - the latter is the most prudent way to go..
Now, your bike is a 2009. The logic dictates that your YES runs until 2014 - so you have quite a while to wait to worry about having to fix it yourself if Yamaha does not. If you don't have a YES, then presumably you have some of the original warranty left and you can buy the extension for your $389 and push that date to 2014.