You might want to read up on this renowned "offline mode" as a lot of people cant activate it without first being online, which DEFINETLY is a problem, i've contacted their support about this a 100 times, with no helpful responses at all, it seems to be a deliberate choice so people won't be able to share accounts for offline plays, so fuckem.
Those people should attend some IT lesson 101, because I downloaded a few games on my girlfriend's laptop yesterday, went to offline mode and then
ran them for the first time, and there wasn't any problems with being offline.
The only problem is, and it's quite rare, if steam has scheduled update, then you can't go into offline mode until steam updates. And it's probably because steam is badly written as an application, not because they hate you.