There's a lot of equations that go into this.

• Where are you located? A lot of countries don't enforce laws - Switzerland, Poland, and Spain even permit torrenting for personal use. Third world countries are usually pretty safe.
• What internet are you using? If you're on your own WiFi at home, a VPN is mandatory if you don't want nasty letters. But if you're doing it on, say, Macca's WiFi, you'll be fine. Bit of a dick move if a lot of other people are using the internet, though. It's also worth noting that some internet providers not only prohibit it, but also detect any BitTorrent usage.
• What are you torrenting? More obscure torrents are less likely to have bots scanning for IPs.
• Are you seeding? Seeding and/or uploading torrents without a VPN is insanely risky, because not only does it expose your IP for longer, you're also committing the crime of sharing copyrighted content (which is prosecuted far more often than merely downloading), so unless it's a torrent that's close to dying, your best bet would be to leech and run.

It's also worth noting that there are ways to download from torrents without even having to run a client.