ORIGINAL: avg_joe
I really don't believe it is corrosive, and eats bearings. If anything, it may contribute to early bearing failure, due to washing away all the oil. WD-40 displaces moisture, this is true. But it also displaces oil.
And just because Traxxas recommends it, doesn't mean it's the right way. That is a company that I wouldn't trust to give the whole answer, or the right answer.(Just ask them how much oil is in their fuel)
WD 40 does not harm bearings - at least not the metal parts. There are certain plastics and rubbers that will deteriorate when exposed to petroleum based products so WD 40 could cause some bearing seals to deteriorate. So, no, WD 40 is not corosive to metal parts but it can be to some rubbers and plastics. That's why I won't use it as ARO.
Nobody is asking you to trust Traxxas but you should pick a different example than oil content in the fuel. There are other, highly reputable and reccomended fuel manufacturers that refuse to publish the oil content in their fuel also.