Mistake 2: Collecting Data "Just in Case"

Mistake 2: Collecting Data "Just in Case"

The traditional approach of collecting as much data as possible for potential future use directly conflicts with privacy principles. Developers often add fields to forms thinking "we might need this later" or enable comprehensive tracking because "the data could be valuable." This over-collection increases privacy risks, compliance complexity, and data management costs without clear benefits.

Common examples include collecting full birthdates when only age verification is needed, requesting phone numbers for accounts that only communicate via email, or tracking detailed user behavior when aggregate metrics would suffice. Each additional data point collected increases the attack surface, requires additional protection, and must be justified under privacy regulations.

// ❌ Bad: Over-collection of data
const userRegistrationSchema = {
  email: { required: true },
  password: { required: true },
  fullName: { required: true },
  dateOfBirth: { required: true }, // Why do we need this?
  phoneNumber: { required: true }, // Not used for anything
  address: { required: true },     // No shipping involved
  gender: { required: true },       // Irrelevant to service
  income: { required: false },      // Definitely not needed
  interests: { required: false }    // Vague future use
};

// ✅ Good: Minimal data collection
const userRegistrationSchema = {
  email: { 
    required: true, 
    purpose: 'authentication_and_communication' 
  },
  password: { 
    required: true, 
    purpose: 'authentication' 
  },
  displayName: { 
    required: false, 
    purpose: 'personalization',
    default: 'Anonymous User'
  }
};

// Collect additional data only when needed
function collectDataForFeature(feature) {
  const requiredData = {
    shipping: ['address', 'phoneNumber'],
    recommendations: ['interests', 'browsingHistory'],
    ageRestricted: ['birthYear'] // Not full date
  };
  
  if (requiredData[feature]) {
    return requestAdditionalData(requiredData[feature], {
      purpose: feature,
      retention: getRetentionPeriod(feature)
    });
  }
}

The solution is adopting a "privacy by design" mindset where every piece of data collection is questioned and justified. Before adding a field, ask: What specific purpose does this serve? Can we achieve the same goal with less data? How long do we need to keep it? Document these decisions in code comments or design documents. Implement progressive data collection, requesting additional information only when users access features that require it.