What are the reasons behind pool transactions fees and what are the consequences? Few days ago I have read this.

For people who are too busy I will try to explain what is written there (this is my understanding which might be wrong, so if you think that it is incorrect, please edit it):

Because of a lot of micro-payments from satochidice, the blockchain has reached a reasonable size and pools are thinking about implementing transaction fees.

Is it possible that at some time major mining pools would decide that they are not going to validate transactions if fee is less than something and thus would be dictating their rules?
Transaction fees have been a part of the Bitcoin protocol from the beginning. They are a core part of the protocol and are designed to be the long term incentive for miners.

And, Yes, miners will often exclude transactions without fees (or give them a lower priority). It's been that way for a long time although it does seem to be getting more common in my opinion.

Satoshi dice has indeed had an effect on the network, but transaction fees have been a part of the protocol from the beginning. The consequences of fees are many, too many to discuss here, but include the motivation for mining (especially as block rewards decrease) and protecting the network from spam and attacks.