Are you looking for the safety of fermentation in general or of vegetables specifically? If it is the latter, then as long as salt your vegetables and have them submerged below their own juices or a brine, then you really don't have anything to worry about. The salty environment inhibits pathogenic bacteria from multiplying as the lactic acid bacteria begin to acidify the vegetables (the lactic acids further protect and preserve the vegetables). So there is no need to fear vegetable fermentation.
There's no need to fear any form of fermentation but there are some important precautions to take when fermenting meats and dairy.