The slice of lemon in a Corona is in no small part to mask the skunkiness (for those of you on the British Isles "cattyness") from packaging the beer in clear bottles. Here's a little-known fact for you. The hops in beer react with sunlight causing a chemical change that produces that well-known skunky smell and taste. Actually, it doesn't just smell like a skunk, it's the exact same compound as the one in skunks. Brown bottles help filter the light to reduce skunkiness. Green and clear bottles do nothing. That's why so many great European beers taste and smell like crap when they come over to the States. Some even call that the "import flavor," not realizing that that is NOT the way the brewer intended.
Some time try this comparison: buy some Heineken and Corona. Buy some in bottles and some in cans. They won't taste anywhere near the same. The can will give a much truer indication of the intended flavor because light can't get through at all.
Thankfully, shippers have gotten much better in the past decade or two of getting beer here more quickly and more well protected. I wish everybody would quit using green bottles but many consumers feel that a green bottle denotes quality or an upscale beer.
uke: 
