The phrase "become numerous" is correct and can be used in written English.
It is typically used to describe a sudden or significant increase in number or quantity. Example: "As the company expanded, their employees became numerous, filling every available desk in the office."
Persuasive technology systems will become numerous and eventually becoming part of everyday lives, at home and at work.
These constitutive equations provide a complex mathematical formulation and become numerous challenges to find numerical and analytical solutions.
"Reporting lines have become numerous and blurred," said the analyst Mr. Morton.
In other polymers the branches become numerous and cross-link to other polymer chains, thus forming a network structure.
But when the beetles become numerous enough, as they have in recent years, they can swarm a tree in such numbers that they overwhelm those defenses.
My prediction is that, in the short term — between now and at least 2012 — this spirit will dominate the Republican Party, until the doubters become numerous and brave enough to make trouble.
The break-ins at my home and flat became numerous.
They became numerous in the Oligocene as large animals with molariform premolars.
After 1000 bce, organized sedentary farming communities became numerous, and active commerce and communications developed among them.
Helicostomella subulata, for example, excysts in June in temperate waters and becomes numerous from July through October.
Only later when the rail crossings of the international boundary became numerous and the generally unsatisfactory example of the Grand Trunk was fully understood were the broad Canadian lines narrowed to the standard gauge.
