The social networking. Whoever introduced this concept possibly didn’t know how helpful it could be in the future. It can be like life - saving drug at times but too much of anything is bad for health.
I have been introduced to this by Orkut in the beginning of 2007 and in the next 2 years, joined many others including Facebook. As the time passed, all others faded away and I am left with Facebook only now. Its called the addiction.
Its getting updated week by week and since the time I have joined it, it has changed a lot. With so many features(I won’t count them to get you bored, most of you already know them well) and so many active users, anyone would find this irresistible.
The large no. of pages and groups(and counting) would surely entertain you as well as educate you.
Earlier I used to find it difficult to use, but now it seems well organized, everything at front.
The mobile sites of most of the companies are trimmed down version of their full sites with some features lost, but FB mobile is no where less than the full site. Its being regularly updated too.
If you don’t find anything to do, start FB-ing.
[Updated 19-04-17]
Got bored, deactivated.
Few weeks ago!