Intriguing - googling around I also saw the $51B number mentioned in http://www.networkworld.com/news/2011/032011-att-tmobile-acq..., and in contemporary articles http://www.photonics.com/Article.aspx?AID=6715 and http://www.economist.com/node/449273 - but interestingly both appear to be written before the deal closed. On the other hand Wikipedia offers no citations for the $24B number.

This is a massive discrepancy - wonder where it's coming from...

edit: the $24B figure was introduced into Wikipedia in July 2007: http://en.wikipedia.org/w/index.php?title=T-Mobile_USA&d... and not challenged since. On the other hand the main T-Mobile article gives a $50.7B figure with a citation. I [citation needed]-ed the $24B claim, let's see where it goes.