Silly Question about iPad 3G and Sim Card

[Wicked1]

Ok, so are the SIM cards for the iPad 3G and iPhone 4 different, or can you use your iPhone SIM card in an iPad, because I would rather not have to pay seperately for two data plans?

 

[deeddawg]

Couple of existing threads found with a quick search for "+iphone +sim"

Can I use my iPhone sim card in the ipad?
Warning: Beware swapping iPhone 4 sim into iPad 2 for data usage

Basically it seems a "YMMV" situation, might work, might get a nastygram from AT&T.