It is far and away my favorite artwork for the books, and I had to do some searching to get those particular editions.
The Terrible Secret of Tom Bombadil
Original Post: http://km-515.livejournal.com/1042.html
Hacker News discussion: https://news.ycombinator.com/item?id=9982237
(Tom Bombadil part starts at 10:58, but the Balrog segment is interesting too)
It is clearly indicated that Bombadil is friends with farmer Maggot (Tolkien states that Bombadil is a Hobbit name). Merry says that Maggot used to go into the Old Forest. If he did so, then meeting Bombadil would be very likely.
Gildor's friends apparently sensed the great urgency, so they would have taken a very direct path which would have led them straight through the Old Forest (after all, Elves have little fear of such things).
The statement that Elrond "has never heard of Tom Bombadil" is clearly wrong given Elrond's comments about Bombadil at the council.
> In those lands I journeyed once, and many things wild and strange I knew. But I had forgotten Bombadil, if indeed this is still the same that walked the woods and hills long ago, and even then was older than the old. That was not then his name. Iarwain Ben-adar we called him, oldest and fatherless. But many another name he has since been given by other folk: Forn by the Dwarves, Orald by Northern Men, and other names beside. He is a strange creature, but maybe I should have summoned him to our Council.’ -- Elrond
Likewise they are wrong about the danger. The Old Forest is not particularly dangerous (as the Hobbits showed by burning part of it down) and while the Barrow Wights (sent by the Nazgul witch king) are dangerous, they seem to hardly compare in danger to caves of dead spirits, haunted pools, orcs, trolls, etc. A war of Gondor against all the evils of Bombadil's domain would be over almost as soon as it started.
I know of no statements that the Withywindle is cursed. Goldberry met Tom there though, so it is likely he sticks around because she cannot leave her river. There is even less evidence that willow trees can appear human (plus the truly bad tree is an "Old Man").
If (like many conjecture) Tom (and perhaps Goldberry) is the physical manifestation of the spirit of Middle Earth itself, then it makes sense for him to withdraw to that area. Arthedain remains relatively undisturbed throughout the third age. The Old Forest and Barrow downs are unoccupied (save for a few Wights) and the Hobbits are a people who prefer the Earth. In fact, almost the entire area of Eriador is unaffected by the War of the Ring save for the Scourging of the Shire (though a big event for Hobbits, it hardly compares to everything else that happened).
To quote Otto from A Fish Called Wanda, "Disappointed!"
Two, four, six, eight
Tiptoe, sneak and infiltrate
Cha cha cha!
It was still quite funny, even though I didn't understand what the heck it was parodying.