What’s “walletconflicts” in listtransactions method output

Here’s an output of listtransactions method

[
{
"account" : "",
"address" : "mz2A28GQxWrYgMn2z9pRqaUFNqTMyhk1sJ",
"category" : "receive",
"amount" : 6.30000000,
"confirmations" : 157,
"blockhash" : "00000000befa3ef184f6c3cdec8814b945bad9e3f7ce9eb38e3102bcf4c030c0",
"blockindex" : 9,
"blocktime" : 1397675516,
"txid" : "f517350f088d235878ecab8d5241f0b6e59a4081eec22031c449d0d01d79ed66",
"walletconflicts" : [
],
"time" : 1397672026,
"timereceived" : 1397672026
}
]

what’s walletconflicts, it’s array of what ? transaction ids, maybe ? i couldn’t find any documentation even in Bitcoin console.

Do physical bitcoins or altcoins actually carry value?

This question establishes that there are physical bitcoins that can be bought and I recently just bought a physical Dogecoin as a trinket but I can’t help but wonder if there’s a solid value related to these coins.

Bitcoins can be found for 1, 10, and 25 BTC and I just bought my Dogecoin coin for 10 USD (18947 Doge after shipping and handling). If someone were to hold onto these coins for years and attempt to sell later on, what would they be worth? Is a 1 BTC coin always worth 1 BTC or, like a collectible, is it only guaranteed to be worth what somebody will pay for it?

I know it’s not officially backed or anything, but is it reasonable to think that if I bought it for 1 BTC that somebody else would pay me 1 BTC for it later even if the value of BTC changes?

Can I download blockchain updates from somewhere?

I use Bitcoin only on rare occasions – say once every month. I want to avoid long waiting times for downloading and verifying blocks that consequently await me when I reopen bitcoin-qt. There are many options available for downloading the whole block chain when one starts out (like the blockchain torrent or the blockchain on Sourceforge). However, these options are full of warnings that tell you they should NOT be used when updating the block chain on an existing wallet but rather only when installing from scratch.

Are there similar ways of more quickly updating the blockchain by downloading recent blocks from some other source?

Note: I am not looking for other clients, but specifically for alternative blockchain download options for bitcoin-qt.

How to stream transactions on the network

How would I go about getting a stream of transactions broadcast on the Bitcoin network? Is this supported by the vanilla client?

I know that the client can notify me on new blocks and on all transactions that effect an address in my wallet, but I want to stream ALL transactions on the network.