Once upon a time, the way to get a patch into the mainline kernel was to email it to Linus Torvalds. A hopeful developer would then wait for Linus to release a new kernel tree to see whether the patch had been included or not. In the latter case, the more persistent developers would resend the patch. Often, developers had to be persistent indeed if they wanted their code to be merged. The system was, in other words, lossy; we'll never know how much useful code was simply dropped.