A couple of you guys have me beat by a long shot. I haven't had the pleasure of being given a tiny practice amp masquerading as "backline", but I have a few friends who have.
For the past 30 years or so, off and on, I've played with a hard/rock metal outfit whose heyday was the early '80s. The band still has a following, and still sells records, if only now from the merch table and online. Since about 2006, every summer, we've got together for a few weeks and gone to do a bunch of shows, either here in Canada or Europe. These are really the only "fly" dates I do; the rest is local and I bring my own rig.
Anyway, with this band, I'm usually very specific when it comes to backline, so I usually get what I want. The only real disappointments that come to mind is that everytime I play Ottawa (Ont Canada), I always seem to get stuck with the same Yorkville XS400 2x10 combo with a Yorkville extension cab. Everywhere else I get my SVT/810. I'm an Ampeg guy, so while I was able to coax a somewhat usable tone out of it, and it was plenty loud, you can imagine my disappointment with the Yorkville.
And then there was the Open Air in Germany in 2012. First disappointment was that my bass did not arrive (it was never transferred to the international flight due to a thunderstorm in Toronto), so, being left-handed, ended up using the only lefty I could find (a $200 Ibanez SoundGear), and the backline amp was a Marshall bass amp (some rack-mounted POS) with a 4x10. Needless to say, it sounded like sh!t to me. Marshall should stick to guitar amps. Actually, I think their bass stuff is discontinued now except for the "student" stuff.
BTW, Clammy - I think we may have met in person - I was an Ottawa boy for years, and I've known John Ricci just about forever...