One other thing to consider - many here are stating that ultralights "aren't" registered. This as I read from the EAA is incorrect.
It is true that ultralights don't register with the FAA, but ultralights can be registered through the voluntary registration system provided by the EAA. More than just issuing a registration number the EAA states the number should be on the ultralight's tail just like an "N" number. The EAA also states the registration as well should be used when making radio calls. The number however is not an "N" number but instead is an "E" number very similar to the "N" number format. Instead of keying up at a non-towered airfield with "Field name, Ultralight entering down wind for runway xyz, Field name" the pilot would state the ultralights manufacturer such as "Field name, Badland Echo 8743 Alpha Romeo, entering downwind for runway xyz, Field name".
Since there are transponders and ADS-b that are extremely small and even a few that use Bluetooth to connect to a phone or tablet, the question is would this be allowed and can the "E" number be used instead of the "N" number?
Add on to this, if the answer is that this would be allowed or isn't prohibited would an ultralight with such equipment be allowed to file flight plans and request flight following?
With the technology jump over the past 10 years, safety equipment like this has become smaller and cheaper. The same can be said for ultralights which are once again becoming popular because of their low cost. I need to add the the EAA will not just issue an "E" number on request. There are pilot training requirements with a CFI before the EAA will issue the registration. This to me is ideal and similar to how amateur radio operators have been self regulating for years. It's the right direction to go for ultralights since the FAA changed the rules for SLA aircraft and almost killed ultralights.
I can see this voluntary system of registration come into play along with the use of transponders, ADS-b, other safety equipment, allowing flight plan submission, and flight following a major benefit to ultralight pilots looking at upgrading to SLA or PPL. I'm certainly not advocating to allow ultralights to have the current flight restrictions changed. Those limitations should remain, but allowing any type of flying machine to use identification equipment helps everyone in the air as well as those that control airspace.
If you don't think so then I ask the question, why do all with the exception of the very smallest drones (UAV's) need ID systems now, but not ultralights?