Getting the law (or even policies on prosecutorial practices) changed to prevent another such incident is a VERY HARD task. Taking small steps toward that task is NOT "meaningless".
The victory to be celebrated here is NOT that the problem has been solved. It is not even that the White House now has to help work to solve the problem. The victory to be celebrated here is that the White House actually has to say something. (And they DO have to... if not, then the press coverage will increase until reporters demand an answer on their own. Heck, refusing to comment would be GREAT for our cause.)
Do you have any idea how difficult it is to make the White House at least make a statement about your issue? It is something powerful lawmakers and world-spanning corporations often find themselves unable to accomplish.
Now, that's not much: the White House's response may consist of meaningless blather. But it is not nothing: the White House has been forced to respond. And it helps to increase the momentum toward taking some kind of REAL action.
The petitions at WhiteHouse.org don't fix problems, but when something is NOT being discussed by lawmakers, this kind of thing can help get that conversation started. Belittling it isn't helping.
And they DO have to... if not, then the press coverage will increase until reporters demand an answer on their own.
No, the media coverage will the same as it has always been since Obama announced his candidacy: fawning adoration, mixed with just enough mild skepticism to create the impression amongst themselves and others that they really do perform some sort of journalistic function and that what we see in the media really is "news" and not just propaganda.
Poke a Mainstream Media "reporter" deep enough and you'll always touch MSNBC.
What a skewed view of the world - I hardly think you will find MSNBC by poking FOX reporters, NYT reporters or Christian Science Monitor reporters (not to mention al-Jazeera, BBC, RT, etc.) And Obama has gotten plenty of bad press.
I hardly think you will find MSNBC by poking... NYT reporters or Christian Science Monitor reporters (not to mention al-Jazeera, BBC, RT, etc.)
I assume this is a joke, particularly the NYT. And I'm not seeing ABC, CBS, NBC (owned by GE, which has gotten massive "green energy" subsidies from Obama), PBS, the former Current TV, not to mention almost every newspaper in the US, anywhere in your list. Kinda lopsided, huh?
As for the foreign media organs, the BBC, al-Jazeera, and RT are all famously anti-American. Obama still manages to get much better press that any Republican. They hate America and they like Obama. Odd.
I suspect that _just signing_ a petition almost creates no impetus for change. The whitehouse response, while it might get some attention, is just that - a PR response. if everyone who signed the petition instead wrote a letter to their respective congressman/woman , it might've affected some more changes.
I don't want to belittle the petition, but it makes it look like change is being afected, while in actual fact, it is nothing more than managing PR for the whitehouse.
Not only that. Just last month Carmen Ortiz was being talked up as a serious candidate to be the next governor or AG of Massachusetts. 
Now she is extraordinarily unlikely to ever hold elected office. I know that I -- a committed Democrat -- will cheerfully send money to any opponent in a primary and even an odious Republican in a general election running against her. The local tech scene is full of people who feel the same and can organize the state's most productive industry.
One US attorney on the verge of greatness has seen the career consequences of serious misbehavior. We can only hope more will see them because the nation's prosecutorial culture is nasty, vicious, anti-democratic, brutal, and out of control.
As you say, many responses have been meaningless, but this contradicts your point: it is indeed a force if they express a preference on the issue, and their lack of stance on many topics reveals that words have consequences. There's nothing wrong with calling Obama out on this, even if not much results, because the population will realign if Obama takes the opportunity to advocate for a difference from the status quo.