Words don't often fail me...

[Mich the Tester]

I am with you here, but I'd add that it doesn't look like kidnapping for ransom, it seems to be to keep them in a "good" "muslim" environment where they will not get educated or otherwise "spoilt" by western influences. I.e. they have not been kidnapped, they have been enslaved. I'm OK with the idea of going and freeing slaves.

I think if anything they're trying to show who's in charge; it's a direct assault on the power of the state of Nigeria and the (usually pretty reasonable) rulers of Borno. Boko Haram looks like a comeback by the followers of this lovely chap; Maitatsine - Wikipedia, the free encyclopedia who believed he was a prophet. He caused quite some trouble in the 70s.

In other parts of the north, Boko Haram have been active but their brand of Islam doesn't seem to catch on in the parts (most of the north) which fell under the Sultans of Sokoto before the colonial times, perhaps because Mohammad Bello, the second Sultan and his sons were known as peacemakers who brought education and rights for women. I don't think these guys have an awful lot of support; Nigerian muslims are not generally aggressive about forcing their beliefs on others. Even though there is officially Sharia law in much of the north, non-muslims live there and can buy a beer in most towns as long as they don't go around drunk, women can work, own businesses are not obliged to wear islamic dress, and vote in elections and have access to education, which is perhaps what these guys find most objectionable. The current Emir of Kano actually did a lot to introduce western style education in his region and unsurprisingly, he's a target for Boko Haram too and now apparently lives surrounded by armed guards even when he's in bed. It's not so easy to oppress people who can read, write and communicate their opinions to others. The trouble is, you don't need very many heavily armed psychos to take control of a large area.

Interesting little detail is that a couple of years ago, oil was found in lake Chad. It wouldn't surprise me if there are some economic interests in this too.