Lets keep the "doomed" part short : my answer would be iPhone (and it's siblings).
This is why : ban it from the company’s internet access makes no sense, as a growing number of your people will reach facebook anyway from their phones.
You waste just as much time on a phone than on a computer.
Ok, now, why is banning facebook bad decision?
Most of the companies I meet with want to know what they could or should do using social media and Facebook in particular.
Well, of course you want to hear more about the website which has about 300.000.000 members (by the way, the 5 biggest Facebook countries are #1 USA - 81M, #2 UK 20M, #3 Turkey 14M, #4 Canada 13M, #5 France - 12M)
According to Universum, 88% of French master degree students (and equivalent) are on Facebook so whether you like FB and the hype around it, or not, you have to consider it for its advertising potential and interaction.
Chances are, no single website will gather a larger portion of your audience when it comes to millennials.
Now you just have to figure out how you can put Facebook to good use within your HR marketing strategy ... and that's when it gets complex.
According to an (already old) survey, 50% of US companies seem to ban Facebook from the office.
Are those companies willing to ‘look cool’ although they're not?
Of course, there's the fear those highly qualified employees, selected to shape the future of multi million dollars companies, might not realise the money they receive from their employer is not meant to fund their time on FB ...
I mean ... really?
A client of mine formulated that very sensible theory : "I think when the first phones in the office came, management would not allow just anyone to have one because those people would be so overwhelmed with being able to give phone calls to people that they would do it all the time; its probably the same for social networking, it needs time to settle as something people will know how to reasonably use" (Vincent, if you read me, thanks).
There are risks you should consider if your company is one of those 50% though ...
1st, assuming you chose to use social networks as part of your HR marketing (which you definitely should by the way), you risk disappointing new hires by selling them what you're not (how come social networking is cool enough for the company to use as part of it's attraction strategy but not enough for them to use as employees?).
2nd, you'll end up loosing some of your employees. This Accenture survey (USA, Nov 08) called "New generation workers want technology their way" is a MUST read.
I'll just quote their conclusion :
“The message from Millennials is clear: to lure them into the workplace, prospective employers must provide state-of-the-art technologies,” said Gary Curtis, managing director of Accenture Technology Consulting. “And if their employers don’t support their preferred technologies, Millennials will acquire and use them anyway. In order to acquire and retain the best talent, organizations must understand the technologies that the new workforce expects and then find a way to support their employees without compromising enterprise security.”
If that's not enough, I'll quote another survey (and, by the way, I just love quoting surveys) that found out that "39% would consider quitting work if social networking was given the chop."
With the rise of the Blackberry powered "Nights & week ends working availability", workers have long learnt that they had to keep room for work within their personal time, now they want to right to slice some personal into their work time : "I'll stay in the office until 8PM and then go to my friends place for dinner afterwards assuming I had the chance to plan it on Facebook during the day (20 minutes?) ; otherwise, I'll just leave at 6 and plan the exact same dinner ..."
So, i beg you "Don't ban Facebook at work" (and yes, that’s another survey!)
PS : Assuming you work for one of those companies, you obviously have tried replacing "http://" by "https://" at the beginning of the URLs when trying to access Facebook? (works more often than not).