[daftypatty]

For example, for an alcohol, why can't alcohol theoretically act as a base and receive a H proton on one of its lone pairs to form a conjugate acid? It still has an octet of electrons, but it would have a formal charge of +1. NH3 can gain a H atom and withhold a formal charge of +1 so why can't oxygen?

[Radu]

 But it can, indeed! What do you think it happens when mixing ethanol with HCl? or with other very strong acids?
   Moreover, an oxygen can form even 4 bonds. Think of Be₄O(AcO)₆ structure.

[orgopete]

But it can, indeed! What do you think it happens when mixing ethanol with HCl? or with other very strong acids?
   Moreover, an oxygen can form even 4 bonds. Think of Be₄O(AcO)₆ structure.

See http://en.wikipedia.org/wiki/Basic_beryllium_acetate