I remember wondering if buying alternate domain names was really necessary or just a marketing gimmick. At first, I passed on it, but then a competitor scooped up a variation of ours and ran ads against it, which created a lot of confusion for sellers reaching out. We ended up buying the additional extensions and misspellings to prevent that from happening again. Generally, you're in good shape with just a strong .com, but if your business is growing fast, it's worth locking up the main variations too.