This is a legitimate worry: There are plenty of reasons you might not want all your Snapchat friends to know where you are at all times. Thankfully, this problem is one that's easy to work around. The Map gives you the option to be completely invisible with Ghost Mode, or to be visible to select friends only.
However, there may be an unintended consequence of remaining visible, even to your closest friends: If you're avoiding responding to a message, others will know. When you tap on someone's Bitmoji on the Map, you see a timestamp indicating when they last opened Snapchat. If you're waiting on a response to a text that you sent two hours ago, only to see that a friend was on Snapchat an hour ago, the jig is up.
This adds another dimension to Snap Traps, a phrase used to describe the social offence of looking at a friend's Snap, but not answering their text.
Naturally, the Snap Map timestamp isn't a foolproof method for discovering that you're being ignored, especially for messages sent outside of the app. There's a chance that your friend opened Snapchat without looking at their texts or missed calls. However, since the timestamp automatically updates when you go into the app, it's a better indicator of someone's online activity than an app like Facebook Messenger. Although Messenger has read receipts, it's easy to get around these by enabling message notifications.
All of this plays into the larger complications that come with being constantly connected. If you have accounts on Facebook, Instagram, and Snapchat, the only way to go completely "offline" is to avoid posting, commenting on, or watching anything, and, in Snapchat's case, activating Ghost Mode or leaving the app closed.
Otherwise, prepare to face the wrath of the ignored.