There's no right or wrong answer. I've lent my trailer out several times to several different people. Most people I know well, others I should of known better but felt bad saying no. Sometimes it comes back perfect, other times with a huge scratch from the front of the trailer to the back, blown tire from going 85 on the freeway in 95 deg weather, broken triming on the inside, most recently a huge dent. I've never chargeed anyone, the guy offered to pay for the dent but said he didn't know anything about it (which is possible because he had it parked on the street). I told him not to worry about it since he didn't know about it. Probably being to nice. If I was him I would of made sure I paid regardless if it was my fault or not simply because it was in his care. What ever. ..
Bottom line for me, I'm probably done lending my trailer.