Speaking in a more realistic viewpoint to the rather black and white way this is being looked at, ICS is still a good strategy but is in many ways harder and requires more thought than staying small.
As others have mentioned the fact of large borders and an early strain on happiness is a major sticking point but if you plan ahead i never really find this much of an issue. I tend to run out of spaces to plant cities in worthwhile spots more than i find i don't plant a new city due to happiness. I usually play a huge map with 19 civs including me and all CS's, on a medium sea level and on immortal (game composition matters when referencing how many cities you build) and i tend to plant 10-15 cities depending on my start location and what land is around me as well as how close my neighbours are. I stop building cities when i run out of places to put them.
The key for an ICS style strategy is to grab as many luxuries and strategic resourses as you can during the initial expansion phase in particular as luxuries will help greatly with happiness and any extra can be sold to buy units for defense and rapid expansion.
Grabbing strategic resourses also alows you to have personal access to resources to build a well equipped army and often plenty extra to sell on to again help buy more units for defense and rapid expansion.
Early DoW's from neighbours can be a problem but again as long as you plan for them then they can be an advantage. Concentrate on building an adequet army to fight at least two wars at the same time with a general rule i follow of having at least one archer and one warrior per border city. Early on i tend to go two warriors and one archer, with the archer obviously stationed in the city but as i grow and connect up cities with roads i tend to aim more for a 1-1 ratio as nearby units can deploy to an attacked area quickly to help defend rather than each city having to hold out by itself for quite a while.
As you grow, horse units become more useful due to their high movement points and thus ability to quickly reinforce areas under attack.
As long as you have a decent army any DoW is actually a blessing as it allows you to train your troops as well as often push for a favourable peace deal or even take some of their cities to further expand.
Unless they have a particularly juicy city i tend to just push for a favourable piece deal in early wars where i can milk then for gold and resources to help fuel my expansion.
The gold is most important as it is yours, the resources should be seen as no more than a stop gap as they are pretty much guaranteed to DoW you again once they rebuild their army and this is why i am usually not so rushed to take their cities as i know they will DoW me again in the future and i can take their cities when i have stopped building my own cities due to running out of spots to place them.
These early wars are often a source of free workers also which help you to more rapidly connect and develop all your cities.
As i mentioned at the start though this should be looked at realistically rather than in a black and white sense. Building a new city ever 4 tiles no matter what is not a good idea in most cases as you will often find yourself in pointless areas like the middle of a dessert or a mountain range and also you can often move a city 1 or 2 tiles away and have a vastly superior city location.
It is much more a case of grabbing as much land and resources as possible to give yourself a huge base to work up from. Your creating a large gold producing empire with large cashflow from all your trade networks and from selling all the excess resources you have available to you.
Plant cities in prime locations and locations with resources, then back fill as necissary to join up your empire.
Again looking realistically, Camikaze mentioned the production penalty, which i assume is meant from high unhappiness. Spamming blindly is just like placing a city every 4 tiles whatever the location is like. You need to use a bit of common sense and flexibility and you should aim to keep happiness at a managable level rather than spamming your way to crippling unhapiness.