Legally, it's presumed valid. It may be easy to prove that the invention is not novel, but doing so would still involve time, effort, and money. The patent holder needs only to settle for a smaller amount of money than would be required to invalidate the patent.

Exactly. Many smaller businesses can't afford a lengthy legal battle even if they are likely to win.

Lady justice's scales are balanced by cash.

That's why the legal system is wrong.

Sorry, this patent is invalid, but your prior art covers a different invention. Page 19 shows a singly-linked list. Page 20 shows nested lists (a list where some elements are also lists). I don't see anything in this document that covers the same type of multiply-linked lists that the patent claims.

As I vaguely alluded to in another response to one of your comments, the argument could go like this:

1. The linked list was described in 1957 or earlier.

2. The cited mention of the linked list also considers more complex permutations of lists.

3. This patent effectively describes adding a single set of items to multiple lists (I haven't read the patent, so I may be glossing over details).

4. #2 demonstrates that such a permutation of the concept of a list would be obvious to anyone skilled in the art.

5. Therefore, the patent is invalid.

Aside from it being obvious, I'm pretty sure there's prior art for specifically what this patent describes. One of the times this was posted to Reddit someone posted a link to a book that describes pretty much exactly what's in this patent, with a diagram no less. http://my.reddit.com/r/programming/comments/1bbb3/congratula...