A trademark verifies to customers that a product really is yours, which also helps them trust they’ll get the quality associated with your brand.
“No good deed goes unpunished” is a quote of debated origin, but I am reminded of it today.
No Good Deed …
I met Linus Torvalds in May of 1994. I saw in the Linux(tm)  kernel (and associated layered software) a unique research platform for 64-bit algorithms. I facilitated getting a $20,000 DEC Alpha system to Linus so he could give Linux a 32/64-bit virtual address space and make it more portable to both CISC and RISC systems.
By late 1996, I was associated with a small group of companies that believed Linux had deep commercial capabilities, so we formed Linux International(TM) and, with Torvalds, trademarked “Linux.”
Use Express-Checkout link below to read the full article (PDF).