Ongoing neck risks?

[TsPoet]

So, I am careful not to proselytize bents, but this need mentioned here.
One major reason people get into bents are for neck issues. There are very upright bents that completely negate issues, then there are sporty ones that bend the neck the opposite way of a DF, which is (supposed to be) infinitely more natural and better angle.
I thought bents were silly until I tried one. A year after trying one, I'd bought one, 2 years after trying one, I sold my DF. I now own 3, just like DFs there are different styles for different types of rides.

Pros - ergonomics, comfort, aerodynamics are improved (faster on flats and down hills) I'm sure others
Cons - they are harder to transport, they are harder to hang with non bents because the characteristics are different, they are harder to climb with.

If you want sporty something like:
http://bacchettabikes.com/bikes/performance/corsa
The winning men's >50 RAAM 4 man team were riding the high end of this style/brand. They won their class since they were all by themselves, but I'm pretty sure they beat the DF in the same class

If you want a very neutral neck position
http://www.easyracers.com/
these can be as fast as teh above, especially with fairings and body socks.

If you want more info on recumbents than you ever thought you would.
http://www.bentrideronline.com/index.php

[OakLeaf]

How are they on the lumbar spine, though? Seems like it would be really bad, between the seat and not being able to extend your hips?

[TsPoet]

How are they on the lumbar spine, though? Seems like it would be really bad, between the seat and not being able to extend your hips?

You've got to get a seat that fits, but I think that's easier than it is for DFs.
There is something that some get termed recumbutt - which I suspect is a lumbar spine issue. It is (almost?) always cured by a more reclined seat. But, then you get neck issues... but you can easily get a neck rest. Just like DF, you have to find what fits you and works for you. It's easier to do with a recumbent than a DF, though.
On my performance bent, I have a somewhat reclined seat and a neckrest - the combo is wonderful. Fast (for slow old me), but comfortable.
On my commuter bike, I have never had any issues with the comfy seat and recumbutt and my seat is upright enough not to need a neck rest.
Other than recumbutt, I've never heard of back/butt/neck issues on a bent.