Are multi-sig M-of-N transactions with N > 3 supported? BIP 11 makes M-of-N multi-sig transactions standard --- for N &lt;= 3. What is the current support among miners for the multi-sig transactions with N > 3? (say 3-of-6). Also, BIP 11 states: 


  The current Satoshi bitcoin client does not relay or mine transactions with scriptSigs larger than 200 bytes; to accomodate 3-signature transactions, this will be increased to 500 bytes.


Does this still hold, and if yes, does this limit come into play for N > 3 or M > 3? What other obstacles are in the way of standardizing M-of-N for meaningful N?
Standard multisig outputs have max 3 keys, but it is possible to add up to 16 keys.

This limit is probably a result of the hard limit of output script size.

EDIT: source: I don't remember where I found this information. (I implemented it in Dartcoin and put that in the documentation.) As an alternative source, check out Mike Hearn's BitcoinJ implementation here.