Importance of Lay Followers

MindGate

Did the Buddha ever place importance on the existence of lay followers? By this, I mean, did he openly state and stress that for Sangha to exist, that lay followers must exist alongside it (and thus not everyone could or should become a monk/nun)?

BhanteLucky

Here's a nice quick sutta which answers part of your question, and shows how a monastic sangha is totally dependent on laypeople. Without them they would starve to death (well, Theravada monks at least. Mahayana monks are allowed to grow and cook their own food.)

http://www.accesstoinsight.org/tipitaka/kn/iti/iti.4.100-112.than.html
§ 107.

This was said by the Blessed One, said by the Arahant, so I have heard: "Monks, brahmans & householders are very helpful to you, as they provide you with the requisites of robes, alms food, lodgings, & medical requisites for the sick. And you, monks, are very helpful to brahmans & householders, as you teach them the Dhamma admirable in the beginning, admirable in the middle, admirable in the end; as you expound the holy life both in letter & meaning, entirely complete, surpassingly pure. In this way the holy life is lived in mutual dependence, for the purpose of crossing over the flood, for making a right end to stress."

Householders & the homeless
in mutual dependence
both reach the true Dhamma:
the unsurpassed safety from bondage.
From householders, the homeless
receive requisites: robes, lodgings,
protection from inclemencies.

While in dependence on those well-gone,
home-loving householders
have conviction in arahants
of noble discernment,
absorbed in jhana.
Having practiced the Dhamma here —
the path leading to good destinations —
delighting in the deva world,
they rejoice,
enjoying sensual pleasures.

It's worth noting the Buddha never expected or wanted everyone to become monks and nuns. The rules he laid down for who can ordain as a monk are quite tough, and so not everyone would qualify.
Besides, most people would never ever in a million lifetimes want to renounce all that nice stuff they have in normal lay-life. TV, music, great food, orgasms, children, etc etc.

MindGate

That answers my question perfectly. Thanks!