Around here, unless you get sucked into doing a "benefit" (the benefit being, of course, to some party other than the band) a group is expected to bring their own PA, instruments, amps, drums, and lights, and play four 45-minute sets. Multiple bands are unusual, but the local college has gigs that feature four or five a night -- these are not "jobs" (i e, paid) so don't concern me.
In other words, almost all my gigs feature my band as the one and only and my bass and rig as the one and only. I do have a story to tell, which should make people aware of the dangers.
I had a long tenure in a dance hall band as the bass player. It was a four piece, but the singer always wanted a backup singer who could sing the occasional lead. He recruited a guy who had been leading another band and was their lead singer. Our guy was happy with him, but friction surfaced when the new guy started to suggest material that he was comfortable with. First of all, he was one of those "I can take any song and put it in three chords" guys. Damned if he didn't prove it, too, to the horror of the rest of us (at our first practice where he brought in a song, he said, "I'll leave out the hard part in the chorus." "What's the hard part?" we all asked. "Well, it goes to Am in the chorus." I swear to God. He didn't like my bass playing, either. His approach to playing bass while singing was to play a rudimentary walking bass line to EVERY song. After listening to me play one evening, he said, "I guess you can't handle that walking bass." It's probably unnecessary to add that the band thought he was a real jackass. The band broke up -- this guy pretty much took the fun out of music, constantly trying to reduce what we did to the lowest common denominator (that would be him) -- and he and the lead player and drummer started a new band that practiced at the same place as me and the original singer and our cohorts. For what it's worth, the jackass's new band was FIRED from the local VFW! I didn't know it was possible to be THAT bad. Anyhow, I had left my Mesa/Boogie Walkabout Scout at the rehearsal place. Between my visits there, the jackass did a practice and played through the M/B. Perhaps I don't need to tell you that a Walkabout has a sophisticated, infinitely tweak-able EQ system, incorporating passive and active boost/cut along with a parametric section. It can take a few minutes to dial in the exact tone, but it is the Tone King, once you do.
The next time I plugged my bass into the M/B, I was rewarded with the most horrible sound I've ever heard from an amp. Our friend the educated jackass had used it (without asking, of course) and turned every knob on the amp to its clockwise limit. To this day (and this happened over a year ago) I cannot conceive of what he thought he was doing.
The Mesa/Boogie went home with me that night.
The lesson? Nothing is foolproof. Fools are too damn ingenious. Don't leave your gear where Stupid will find it, and don't lend it out.