Why the 1MB fetcher limit

[Will Norris]

We're running into some issues in WordPress, where a plugin called  
"Bad Behavior" is not liking the "Range: bytes=0-1048576" header php- 
openid is adding to fetch requests.  Before I push too hard in either  
direction on what needs to be fixed to correct this, I was wondering  
what the rationale was for adding this request header.  Why limit  
responses to 1MB?  Was this an arbitrary size, or was there some logic  
to it?  Why was this added in the first place?  Was the absence of  
such a limit causing real problems?  I'm not necessarily saying it  
shouldn't be there, I would just like to understand what the thinking  
was.

I see from the changelog that Dag added this to the php library on May  
29th... hoping he or someone else could add some insight.

Thanks,
Will