We all have, tremendously. Sadly, Ms. Lacks herself really didn't.
Henrietta Lacks was suffering---indeed, dying---from cervical cancer and being treated at Johns Hopkins, where a researcher by the name of George Gey covertly took one of her biopsy samples and began replicating it in petri dishes---cloning it in a sense, but mostly really using the cancer's own power of exponential replication.
This was the first time anyone had successfully created an "immortal cell culture", a colony of human cells that had the power to grow and multiply indefinitely.
The cell line is now called HeLa (shortened from Henrietta Lacks of course). It has been used for numerous purposes in biology and medicine, from the polio vaccine to space research. HeLa has been used to develop treatments for Parkinson's disease, leukemia, and even influenza. The development of immortal cell cultures was a major breakthrough in medical science.
And of course pharmaceutical companies have made millions of dollars selling patented drugs that used HeLa in their development, and neither Lacks nor her family will ever see a dime of those profits. It is likely that Henrietta Lacks herself never even knew her biopsy sample had been used in this way. Many of her family members were even tricked into giving DNA samples that researchers later used without their knowledge.
Therein lies the paradox: The creation of HeLa was therefore at once a major breakthrough in medical science and a grievous breach of medical ethics. Its benefits for humanity have been enormous, and it is likely that Lacks would have consented to this research if she had ever been asked to---but she was not. Racism and classism clearly played a role in convincing scientists that they didn't need to get her consent in order to use her cells in this way. The good news is that this particularly egregious case has spurred a new debate on medical ethics and informed consent, so that hopefully something like this will never happen again.