I'm of two minds on this question. Perhaps my perspective as a long-retired participant explains my ambivalence:

I would have *hated* to complete with amplified acts back when I was singing unamplified on the street; it was hard enough having to go up against 4- 5- and 6-piece bands! Performing on my own and working with minimal equipment was simply my modus operandi back then, and I felt I needed a certain amount of space, and a degree of quiet, to function. Would I have I gone the amplified route if I could have? Probably not: I certainly could not have afforded the extra equipment, nor would I have been eager to carry it around with me. (Well, poor-mouthing may not an entirely valid response; while I never owned an electric guitar, and would always have found it difficult to buy an instrument with an amp and everything that goes with it, my one unamplifed guitar has always been a good-quality and fairly expensive instrument.)

On the other hand, I am glad to hear, and generally admire, some of today's buskers who do a good job with modest amplification. There are a few guys who seem to pass in and out of town, doing a nice job with electric-style blues; without their little battery-driven amps, they not only couldn't be heard, they couldn't even approximate the *sound* they're working to produce. Also, with amplification, instrumental blues guitar can stand on its own without vocals much more easily than can the acoustic variety, and some of these players do little or no singing. (In some cases, the less singing, the better!)

One interesting variation I've encountered: a fellow I saw several times a couple of years ago, singing Sam Cooke tunes (seemingly) a-capella, and doing a very nice job of it. After catching his act several times on successive weekends, I realized he was doing the same tunes in the same order -- on closer inspection, I observed that he was singing along to a "Greatest Hits" cassette through his Walkman headset!

The worst offenders are those with loud gasoline-powered generators: they have to turn up "to eleven" just to overcome the noicse of their own equipment!