Why NOT. Facebook advertising is the most recommended way of advertising to startups. Reason being, you get a lot of flexibility in deciding your budgets. You can start with as low as $50 to try the response.
Another important take is Organic responses takes more time and comparing it with Man Hours of efforts the advertising is always cost effective. For example 8-10 Hrs of organic efforts to increase reach of your product/brand to audience via groups, one to one messages etc Vs $80-100 spends (considering bare minimum hourly rate of $10/hr). You will see a better response on spends.