There will always be a risk of someone taking your t-shirt design and printing it off themselves.
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My main concern is that people could easily press the printscreen button and/or copy your design and make it themselves, or if they see a catchy slogan they can just take it for themselves and advertise it. Therefore, I am quite hesitant to put any of my thoughts onto these sites. | |  | |  | |
Whether you put it on cafepress, spreadshirt, your own site, no site, or market it locally, someone can take your idea.
Anytime you take your idea and put it out in the public, it has the risk of being copied or misused.
It doesn't happen that often. You just have to take the normal precautions of protecting your intellectual property (research trademarks and copyrights).
This is not to scare you, but to just offer some reality that every single t-shirt you see for sale online is "out there" facing the same risks.
The rewards of selling lots of t-shirts far outweigh the small risks for some shady person taking an idea. Even if they take your idea, there's no guarantee they can sell it better than you can.
Don't make decisions based on a fear of what
might happen, make them based on what you want to happen and do your best to make it happen.