it seems to come down to two main points, as far as consumer tech companies go:

1. GAAP says that revenue from a software service subscription (e.g. cloud service) can only be counted as revenue once the service has been delivered, not at time of sale.

http://www.marketwatch.com/story/ea-to-ease-non-gaap-usage-a...

http://www.grayboxpdx.com/blog/post/revenue-recognition-for-...

2. Equity-based compensation is accounted for as a cost.

http://mercercapital.com/financialreportingblog/equity-based...