LLaMA
Meta released a family of models from 7 to 65 billion parameters, trained only on public data, and gave the weights to researchers.
Why it matters
A smaller model beat one ten times its size, and weights that leaked within a week spawned a whole open-model industry.
Weights were issued on application, but within a week they appeared in the open without Meta's permission. The company did not pursue the distribution, and Alpaca, Vicuna and hundreds of fine-tuned variants grew on LLaMA within months. That broke the assumption that frontier models would stay inside a few companies: fine-tuning someone else's base turned out to cost hundreds of dollars.