Without knowing someones true identity/ background one should probably not be doing business with them. This is why ebay works? You cut your risk down by buying from a vendor that has good ratings.
But you are not doing business with the developers. Sumokoin is an open software project. All the code is available on Github, so there is no need do trust the developers. If you want to run a node or mine you can check the code for yourself (or if you cannot, you can ask somebody you trust to do it for you).
Or if you want to buy coins from an exchange you are then trusting the exchange, not the developers. You have no idea who is selling the coins you are buying, you just trust that the exchange is being honest and you are in fact getting coins that can be withdrawn to your own wallet.
It would be different if there was no premine.
How exactly would it be different? Certainly the premine gives the developers the ability to crater the price of Sumokoin by dumping the premined coins to the market - but such action would make no economic sense. For a new adopter there is virtually no difference between a premine and people who just mined before I did or bought coins when they were cheap.
And most Monero devs are also pseudonymous. Does that somehow taint the Monero project?