I think leaking acid on the phone less of a chance than the much more common problems on ebay: the incorrect battery incorrectly advertised, old batteries which will never have the stated mah, those rejected by the maker for qaulity control issues and sold off brand.
lots of ebay a sellers play fast and loose with compatibility claims. one can see literally hundreds of batteries or chargers listed for multiple phones that use different batteries and chargers from the others listed in the same listing. The ebay sellers know if they sell you one for $10 or $15, and it is wrong, when you look at the time effort and shipping charges of returning them you will just forget about it.
lots of people have success with getting ebay batteries, but many people do not know how to load test mah and don't know when they get one advertised as 1500 mah that is really 1200 mah one that is part of a production lot that was rejected and gray marketed, or a lot that is simply old (and warehouse age can permanently reduce mah.)
same goes with chargers. for example you absolutely want 1000 ma in a car charger since you are likely to be using gps and your screen on full time in a car. That probably is a draw of 500 ma ( you can tell by seeing if that 1500 mah battery will run more than three hours on gps with screen lit all three hours) . there are tons and tons of 300, 400, and 500 ma chargers out here that due to micro sub can be specifically advertised as EPIC chargers. people will get them and wonder why their battery stays flat or actually decreases in charge while "charging."