I can't see anybody ever giving me a taco without receiving some kind of money.
There are plenty of instances of food being used as a marketing gimmick. Churches, auto dealerships, timeshare seminars, etc. Show up and listen to the sales pitch and the food is complementary whether or not you buy.
I realize that's not exactly what you mean, but it's an obvious example of somebody literally "giving you tacos" without receiving money from you in exchange. More relevantly, the internet is full of examples of people providing
non physical goods and services without direct financial recompense. You can download ubuntu, openoffice, google earth for free...you can play flash games on kongregate, listen to music and watch movies on youtube...there's a lot of value that's available without monetary payment. These things are easy enough to provide and there are enough providers that it's possible for these things to be provided without the end user directly paying for them.
It's not such a leap to imagine physical goods like tacos becoming easy enough to provide that a similar arrangement could exist.
whats to keep people from just grabbing whatever they want and putting in no work whatsoever?
Who cares if they do? If you, for example, download some php scripts from a
script library, do you think the authors of those scripts lose any sleep that you didn't "put in work" for it? Of course not. They made them freely available specifically for the purpose of enabling other people to use them without putting in the work to build them themselves.
I suggest we overcome this limiting notion that "work has value" and try to adapt to the idea that results are what matter. If it simply becomes
easy enough to provide physical goods, then physical goods can become available without the exchange of money just like so many non-physical goods already are.
The sooner we, as a society, adapt to this idea, the better. It's not going to be too many more years before an awful lot of work becomes irrelevant. If people remain stuck in the "must work for money to buy food!" mindset, there may come a time when an awful lot of people go hungry.
Some concept of exchange, yes, but not necessarily money.
there are other ways of managing exchange besides money.
Exchange only works when both parties in the exchange have something the other party wants. That might not always be the case. Even if the case of money, there comes a point where I simply have no incentive to give you money for anything you have to provide in return. I can only use so many servants.
Article relevant to topic:
The economics of Star Trek