It is true.
This would have been news about five months ago, but I missed it. So I put it here in the off-topic section. But if you haven't heard, it could be news to you. All the big data carriers are together in a big UNLIMITED data plan scam.

First let me rant about what it means to offer something as being unlimited.
First, a nice restaurant offers an unlimited amount of food for a modest price and then you learn that you have to eat it all inside of 5 min.
Another scam is someone sells you a pass to ride on all the New York subway for a whole month for no additional charge, just as long as you're always going north and not sound.

Sound familiar? How can something be unlimited if you put a restriction on it?

Well, that is what the big carrier companies are doing with the unlimited data plan. It is so rotten that the FCC announced last year a possible penalty. To date, it remains to be seen if the government really will step in and do something about this outrageous ripoff.
Link:
FCC Plans $100 Million Fine Against AT&T Over 'Unlimited ...
http://www.nbcnews.com/tech/tech-news/fcc-plans-100m-fine-against-t-misleading-mobile-data-plans-n377076I don't think your analogies apply.
They are offering unlimited data plans and throttling connection speeds when they are used heavily.

This is like a restaurant offering unlimited food but after you've eaten 5 courses it takes longer to get more, or having a subway pass that you can use as much as you want but after the 5th ride in a day you must always be the last person to disembark from a PASSENGER car.

Not defending business practices, as they are violating net neutrality, just proper use of literary devices.Normal speed on 4G is about 2 to 8 mega bits per second.
But when I go over my 100MB data limit, it droops down to
0.12 mega bits per second.
Not a type. Only suitable for text and some HTML. Downloads break.
Yes, it is like eat all you want in 5 min.
Hard to find an exact analogy. But in any case, one would think the restrictions would be reasonable. In reality that are not reasonable in any way. An throttling is not what they do. Throttling, in common usage, implies a deceleration, not sudden braking.

Others have measured the so-called throttle and found it is not used to improve overall service to users. It is nothing more than a false claim.

I have an account with T-mobile. I have 'unlimited' data over a 4G network USING a common smartphone. Early in the BILLING cycle the thing was very fast. I it slowed down. Actually slowed is not the right word. It was paralyzed from the neck down. The3 I called in and asked for 100MB more data for $3 and withing minutes the sped was up again. Others have reported the same thing. It is about money, not bandwidth.

I urge everyone to read over the pots and reports about
unlimited data scam
The bad reports are not exaggeration. They focus on last year. Just ow they are coming out with a 'new' plan. What was sarong with the old plan?
Just last month:

AT&T brings back unlimited data with horrible bundle deal.

Which is a tacit admission the old plan was distasteful. OK, I bump my own post.
But the story is not over. Some have wanted to do a class action suit only to find they can not. Why? Because the terms of use forbid any class action lawsuit.
Many consumers are totally confused. At some point in time this issue should be clarified.

About the analogy of the restaurant buffet. Yes, they put reasonable limits on what you can eat in one seating. That makes sense.
But data transmission is not really tangible product. The cost of transmission varies a lot. Time of day, Competition, cross-over contracts factor in the real cost. Also they do not really change by what your really use. They change by what they say you use.

This links is from a newspaper in San Jose.
What Unlimited Data Means.