I'm divided on the subject myself. Probably depends on the manufacturer.
In the 90's I bought a 412 slant guitar cabinet with no logo on the grill. It was a Randall, and I suspect the previous owner was embarrassed that it wasn't a Marshall or Mesa, or even a 5150. It worked fine, and I paid about $75 for it. What a steal. Eventually (a few years ago) I found a Randall logo to put back on it.
On the other side of the coin, I have a used Behringer 115 bass cab... and I took the logo off. The aluminum cone speaker resembled a Hartke to me, so why not perpetuate the mystique. It sat under my Hartke 410 anynow, right? Well... now that 15" speaker is dead, and I put in an Ampeg 15" speaker. So I have kind of a hybrid. I want to put a little Ampeg badge in the corner of the grill, just to announce what is inside. I toyed with the idea of a chrome HYBRID car logo in the middle of the grill... but I might just go with the Ampeg plate.
On my G-K Backline head, I took some black tape and did the Midnight Special censoring by covering over the fancy wording "Backline". Doesn't make it look like a normal G-K head as much as it just hides the fact it's the budget model.