First, you need to know from which address you will receive the coins. In many cases it's impossible, because your counterparty will refuse to tell you. Second, there's no objective taint. It's about to whom you will send your coins. Some services might not care about history of your coins at all. Others might hire chainanalysis companies or perform their own analysis. Some services don't want to receive coins linked to gambling. And so on. There's lots of possibilities.