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SMT's are going to increase the value of STEEM, just like ERC20 tokens increase the value of Ethereum. SMT's are quite similar to ERC20, but they are much, much faster and you will be able to trade SMT's to Steem instantly as they launch. This is a very good thing, because when an ERC20 token launches, you must wait until it get's listed on exchanges (sometimes never even happens). With SMT's, you'll have instant liquidity. Thus, more demand for STEEM, which increases the price.

A very comprehensive brief explanation. I like :)

Not if SMTs are not on the STEEM blockchain like @appics said below:

"There will be no connection between Steem and Appics accounts, because Appics data is on the SMT blockchain. Not the Steem blockchain."