Fibrosarcoma with Typical Features of Postinjection Sarcoma at Site of Microchop Implant in a dog (from Vetpathology.org) (english) (Source: Vetpathology.org)
German Institute for risk evaluation: Tattoos not without risks (german language) (Source: Gesundheit.de)
Risks of "chipping" - High costs - Cancer risk (german language) (Source: Protier.ch)
Tumors in long-term rat studies associated with microchip animal identification devices (Source: TheDogPlace.com)
Abuse with allegedly found animals by Short-Message-Service (PDF-german) (Source: DiePresse.com)
Drawbacks of just having the microchip ID:
Some people believe that microchips can be tracked by GPS. That's not true.
The lowest rate for lost pet recovery has ... the microchip (if you use it as single ID-platform).
Microchip-IDs are not visible IDs.
Most people don't know that your animal could have a chip-id-tag.
An animal must be scanned before detecting a chip-id-tag.
An animal must be taken to a veterenarian (or police or fire-department) to get scanned. A lot of police- or fire-deparments don't even HAVE a RFID-Scanner.
After 7pm or on holidays it is very unlikely to find an open facility to scan your animal.
The microchip ID-Tag should NEVER be the primary Identificationtool. Use it wisely as a backup!