It's true that Square's service is no less secure than paying with a Verifone device, sliding your card through the checkout system of your corner store, or handing you card over to the waiter and having them walk away with it in a restaurant. There is one thing that Square has done in a new way though: The service that they are providing, together with their corporate identity, has done a remarkable job at moving the idea of accepting credit card payments from big retail to small businesses and even private people.
While this is an admirable feat, it has has potentially dangerous impact on the users' perception of who is a trustworthy entity to hand their credit card to.
Before Square, I would have never handed over my credit card to a private person that I am doing a one-time transaction with and that I will likely never meet again in my life. With Square's efforts, that emotional barrier is slowly being torn down. Of course, they are not actively telling me to "trust everyone", but it is an inevitable development that they are continuously pushing forward.
Before square, a merchant (a person I would give my credit card to) was usually a person connected to a job in a business entity that was registered, had a (somewhat) fixed location and that was invested into building a long-lasting relationship with me and many other customers (= not interested at screwing me over by doing some credit card scam). None of this applies to an independent person with a square dongle in their iPhone but thanks to Square's efforts, customers feel more and more confident, handing a stranger over their cc for a quick transaction.
This is where there is a problem. It doesn't have to do with Square's technical implementation. It has to do with the inevitable customer's change in attitude, which ultimately, Square is "responsible" for.
I can speak from my experience, coming to SF from Europe and finding a design job at a corporation:
As long as you are not here, or about to come here, you are exponentially less interesting to companies. If they like your email, resume, portfolio, whatever, they want to invite you, talk to you, see whether you are a cool person. And they want to do it fast. This must especially be true to small companies.
Also: You will be able to make so many new PERSONAL connections here, which will make the job search much easier. It's not unlikely to fire off 100 emails to every potential employer and not get much back. But meet one person that you get along with well on a personal level, and you might get your interview right there. Everybody here knows someone who knows someone who wants to hire somebody like you.
(if you need someone to sponsor a visa though, it's a completely different story)