There is a lot of rumour and conjecture surrounding the crash that Alonso had while testing, he will now miss the first race in Melbourne following medical advice.
There is something very peculiar going on, a good write up can be foundhere

There are quite a few F1 fans on here, what are your thoughts, I'm still leaning towards an electrical issue, certainly plausible.

McLaren seem to have denied the electrical issue theory pretty categorically, and I'm inclined to believe them. But it certainly does seem strange that what appeared to be a relatively minor accident should result in such a long hospital stay and recuperation. It's not surprising people are suspicious that there's more to this than meets the eye.

It seems to be centered around the growing awareness of concussion injuries. He is fine to race but the problem would be if he received a 2nd concussion so close in time to the previous one. 
Hung like Einstein, smart as a horse.

I suppose the question is how he got a concussion that doesn't appear on scans, his head is inside a padded helmet that reputably cost in excess of a grand, and he's driving a car with the most stringent deformable structures. We've seen worse accidents and even with the latest caution over concussion it does seem excessive, though higher speeds are in F1, rugby where there is no protection and the rules on concussion are very stringent seem to be fit in a fortnight. my PC is slightly to the right of Genghis
2012 HSE SD4 In Orkney Grey now gone, best car ever.

There is a growing concern, or over reaction?, surrounding concussion injuries, however, that said, this seems to have a stench of cover up, nothing is making sense, especially with the high hopes of Alonso getting Maclaren the much needed.

The speed of the incident, by F1 standards is fairly low.
Vettel's story seems to infer that something happened causing the car to veer off, although other data suggests that Alonso was downshifting on the way to the wall, contradictions at every turn, cameras on the track and car have not been shown?

If it was a benign problem with the car, Maclaren would have put it down to a routine failure expected during testing?
A problem with the driver himself would be covered up.
An incident with the car decapacitating the driver would be covered up.

This incident will go on for a while yet, it will be interesting to see the first race and how many points if any JB will get and jump the lead over his team mate.

I don't get this, are we saying Alonso doesn't have concussion or is deliberately being kept out of the car? 
Hung like Einstein, smart as a horse.

I think we're just saying that the outcome doesn't seem consistent with the accident. It didn't seem that severe, and the car didn't look that badly damaged. We've seen accidents which seemed much worse, with no injury to the drivers.

He may well have concussion, given the furore immediately following the crash and airlifted off suggests something serious and the video post crash seems to suggest he wasn't conscious.

Really looking forward to this season and this is setting intrigue up right from the word go.

There have been other claims of crosswinds that may well have caused him to veer off. Same happened to Sainz Jr - with him it was almost dismissed as a poor excuse for a rookie error (I admittedly thought that) but in light of Alonso's accident seems credible. Now:
17MY Discovery D5 2.0 HSE (Carpathian):

Gone::
(04/17): 16.5MY Discovery Sport HSE (Waitomo)
(08/16): 16MY Discovery Sport HSE Lux Auto (Corris Grey + Black pack)
(11/15): 15MY Freelander 2 Metropolis SD4 (Loire blue)

Didn't pick up Alonso wasn't going to race until I got home from work, bit surprised but understandable given the concerns over the possibility of a second injury soon after the first.

A combination of factors probably at play caused the accident, as is often the case. New chassis, electrics, software, possibly driver error and side winds. These cars are twitchy at the best of times!

Ironically, Magnussen gets to drive instead after he lost his seat so Alonso can join the team. This will set a benchmark against Button in Australia and then we can compare that to Alonso on future races. That's if both cars run long enough!

10 days and counting! 2016 BMW X3 30d SE in red
MY2013 SD4 XS Firenze Red, 19" 10 spoke contrast paint wheels, Signature Strips, Grand Black Lacquer trim, Cold Climate Pack - gone!
2007 TD4 S Stornoway Grey - gone!

If my lotto numbers come up tonight, I know where I will be

He's in a good position to duck his contract, if that is an option he may like to take, lets see how well the car does in Oz, if it doesn't, will the problem still exist in Malaysia? my PC is slightly to the right of Genghis
2012 HSE SD4 In Orkney Grey now gone, best car ever.

Bet Alonso's gutted he missed out on that. 
Hung like Einstein, smart as a horse.