Both the image capturing and facial recognition aspects of the technology are likely to cause privacy concerns. Already Google Glass wearers have had confrontations with strangers who aren't too keen on having their every move tracked or filmed. Google has issued a list of suggested dos and don'ts for Glass users, such as always asking permission before filming or taking photos of people, turning them off in any situation where a phone wouldn't be allowed and otherwise not using the devices in rude ways.
Depending upon how the final product looks and how tiny or transparent the components are, embedded camera contacts could allow users to take photos on the sly with much greater ease than they could with a smartphone, camera or even Google Glass. Anyone's eye could, in effect, be wearing a hidden camera.
There's also the concern that the user data generated by the contact components could get out into the wild. The patent does address the privacy of the wearers, stating that users would be able to opt in or out of providing demographic, location or other personal or sensitive data, and mentions that the device might be able to anonymize any data it collects, receives or transmits. But the privacy of others would, as always, be dependent on the etiquette of the users.
Comfort and safety are other concerns. To avoid obstructing the user's vision, the tiny hardware components will either be transparent or positioned around the contact so that they won't get in the way of the pupil. They also need to be as thin as possible to avoid making them substantially thicker than conventional contact lenses. The contacts would likely be weighted on the bottom to keep them aligned in a certain position on the eye.
Some computing components (such as LEDs) are made out of somewhat toxic materials, so they would have to be coated or embedded in such a way as to shield your eye from exposure. The RF emissions would also have to be kept at or below safe exposure levels.
If they're anything like Google's existing glucose-detecting prototype, the chips that the image-capturing lenses use will be embedded in soft contact material, which should keep users from being able to feel the hardware. People who already wear contacts might find them more comfortable than newbies to contact lenses, of course.