Like I said good way to get robbed.  How do you know the block you got from the network isn't malicious?  You shouldn't be trusting any miner.  The proof of work ensures miners can cheat among themselves however the client "verifies" all the work they do.  If you aren't going to be using the blockchain that is fine.  You simply need to rely on someone else (blockchain server, e-wallet, etc) to verify the blockchain for you.  However the entity doing the validation  ashould be trusted and not some random node on the network there is no way to trust information you get from the network without validating it.  You should assume that anything you receive on the network IS MALICOUS until verified that it isn't.

Assumming blocks are valid just because they are signed is a recipe for getting robbed.  The network works under a "trust nobody" model.  There isn't one piece of data your node gets from other nodes (who may not be trustworthy) that isn't validated.  When your node is sent a transaction it verifies the transaction is properly signed and valid (by rules of the network).  When your node gets a block it not only validated the signature (by hashing the header used by the miner and ensuring the hash matches and is below the target) it also verifies each transaction in the block and then reconstructs the merkle tree to ensure the merkle tree for the block is valid.  Only once all transactions are known to be valid, and the merkle tree is valid, and the block is valid, and the hash for the block is valid does the client consider that block confirmed and increment the confirmation counters.

There is no shortcut.  All that works needs to be completed in order to validate transactions.  This doesn't mean YOU need to have the blockchain but you will need to rely on someone else who does have the blockchain.  For example if you use Electrum client you are relying on the Electrum server to do the validation work for you.  If you use the strongcoin ewallet you are relying on strongcoin to do the validation for you.

Simply trusting blocks as they appear on the network is completely insecure.

Right, don't trust any miner.  But you have to trust > 50% of them.  If the block has invalid transactions it will be rejected by the honest nodes.  If you don't trust more than half of miners, I suggest you go back to fiat or some other model because cryptocurrencies aren't going to work for you.

How is keeping a partial blockchain worse than no blockchain?  That makes no sense to me.  Please enlighten me.  Or perhaps you don't understand what I am proposing?  I never said you can trust a block before it has been confirmed.

So you say you need the entire chain minus pruned transactions?  Funny, that's what I proposed a few hours ago when you first told me I was wrong.  Pruning transactions has no effect on an attacker's ability to isolate you from the network.  Sure, perhaps there are additional vectors once they isolate you, but they can already feed you anything "valid".  So with a pruned blockchain the attacker who wants to send you fake BTC saves himself from having to actually have bitcoins at an address they can send from.  But with a full chain, as long as they have coins they can pretend to send them to you and still retain them or spend them on the real chain.  I will conceed pruning non empty addresses will extend the damage from isolation assuming the scammer isn't well funded, but once you start stealing shit you rapidly increase the damage you can cause to isolated nodes, even with the full chain.  Bitcoin is never foolproof.  Checking bitcoinmonitor, blockexplorer, or some other trusted source is the only way to be sure, and you can bet your ass I do this every time I deal with more than a couple BTC.  I believe your real confusion arises from an overconfidence in the network as it already is.

Yup.  Just need to adapt this for Litecoin.

https://en.bitcoin.it/wiki/BCCAPI

Essentially a server backend which lite clients connect to.  You could have a private backend server supporting a single wallet, or a private server supporting multiple private wallets, or a public server supporting multiple clients.

Can someone explain me how to remove keypairs from wallet.dat?
I need to remove one address . . .

Just one address with like 75k txes 

Thou, I have backup of wallet.dat before spam dusting so I think I can restore it, remove spam address (had just 1 LTC on it) and continue using wallet without a problem 

If you have less than 0.01 LTC in your wallet filled with transaction spam, I would suggest that you just throw that wallet away. Sending those coins will cost you more in fees and further bloat the chain.

Use this to check if the port is actually open in your router/firewall http://canyouseeme.org/

For those of you using the Litecoin p2pool, forrestv has released an update that will make things better. You must update before Dec. 2, or else your p2pool will not work properly. See this thread for more details: http://liteco.in/threads/130-kh-s-distributed-litecoin-pool-using-p2pool.29/

And if you have not tried p2pool yet, why not give it a try?