Thanks for this, Amir.

My initial reactions:

1) This is cool and useful (but see 3)

2) This is significantly less secure than validating an entire blockchain; it's certainly worth working out some use cases here in more detail than just a sample conversation. More on this below

3) What about discovery? Will a client now have the chance to look for NODE_STRATIZED clients on IRC? How do you envision a stratized server decides which transactions to relay/store? Or is it just a caching layer in front of a high quality blockchain service? If it is just a caching service, the question of cache hits / misses is an interesting one as well. 

4) What are the economic motivations to run a stratized server? Other than cheating people of course.

5) Seems like a 'send me everything for this source address' is going to save a lot of roundtrip conversations for what I imagine the most common request will be.

Inre: majority agreement on transactions, and even balances, it would be nice to work out some theoretical security / cost / value calculations for the following scenarios:

Likely value and cost to someone of subverting / lying about

1) An n-confirmation transaction, n > 0

2) A 0 confirmation transaction

3) A NODE_STRATIZED transaction chain for a client with m connections to NODE_STRATIZED servers

4) An address balance request for a client with m connections to NODE_BALANCE_INFO (I made this name up) servers

Peter