All of the above. There is the expectation that you will speak in tongues, and the sincere belief among some of the people I grew up with that it was the sign you were filled with the Holy Spirit (and you weren't saved if you didn't have the Holy Spirit). Some even tossed out the trite little saying, "Fake it 'til you make it" with all sincerity.
Studies have shown that Glossolalia (speaking in tongues) is a learned behavior! It is picked up from those around you. Add that to the fact that you want (and even "need") to speak in tongues and STRONG peer pressure and you have a recipe for conformity. Brain scans of those speaking in tongues showed that activity in the language centers of the brain decreased while showing increased activity in the emotional centers of the brain. Not exactly surprising.
Some of the Linguistic studies of Glossolalia are even more interesting. The Journal for the Scientific Study of Religion has published a large number of studies on many aspects of speaking in tongues. The speakers of Glossolalia only used sounds they were familiar with (this is shown across language groups, with each group using sounds distinct to them), but those sounds, although grouped in recognizable patterns, were disconnected from any actual meaning (separate study correlating with the brain scans showing decreased activity in the language center). Type "glossolalia" in google if you want to do some interesting reading.
It is quite easy to get caught up in the emotional situations you have in a church service, especially for a young person. Being in a church service with emotionally compelling music while a group of people are grouped around you, praying that you will "be filled with the spirit" while speaking in tongues around you makes for some strong incentive to speak in tongues. It isn't surprising so many pick up tongues when it is so easy to learn (again, referencing scientific studies). Once learned, it is quite easy to continue (it can still be done by people who have experienced it, even after disconnecting it from the religion they picked it up from... and it is not a specifically Christian phenomenon).
Hope I answered your questions a little! Did you make it to church?
The verse you mentioned is from 1 Corinthians 14. It's a chapter that talks about the use of tongues in church, prophecy, etc. There isn't any spot that says it's from Satan, although the chapter before (1 Cor. 13:1) talks about speaking with the tongues of men and angels and it not mattering if you don't have love.
I haven't run into any Pentacostal pastors that were as blatantly manipulative as the one you mentioned, but I have heard that it happens. Many are not purposefully being deceitful, they fully believe that they are talking to God and fully accept the fact the people will fall over when influenced by the working power of the "Holy Spirit". Some are just sincere (although misguided) believers who honestly want the best for you. That is the scary part. They BELIEVE, and that belief will guide their every action.
The answer is yes. There have been recordings of tongues and there have been multiple studies done on how it works, who can learn it, how it is transferred, what sort of sounds are used, what sort of structure/syntax/form it has, etc. The results are fascinating and conclude that tongues is an entirely natural phenomenon that is easily learned, contains sounds that are familiar to each distinct person (different nationalities with different natural languages will use different sound groupings in their "tongues"). Different churches who have a predominant number of tongue speakers will have "tongues" that sound similar to those speakers versions (something I have anecdotal evidence of myself) and different sounds than other churches. Again, fascinating results. Do a search for glossolalia and you can come across some great info.