It is permissible to offer sacrifice through some community based companies or enterprises or those available on the Internet because a Muslim can delegate others to offer sacrifice for him. However, he needs to observe their credibility, honesty, and piety so that he would not be cheated by some deceptive ones.
Below is the response given by Sheikh Muhammad Nur on this issue:

Udhiyah (sacrifice) is a confirmed Sunnah from the Prophet (peace and blessings be upon him). A Muslim can make sacrifice by himself or appoint someone else to do it on his behalf, as many people do in Hajj in paying an organization or institution to slaughter the hadi (sacrifice in Hajj) for them.

Scholars of Islam have said that it is allowed for a person to make the sacrifice by himself or appoint someone else to do it on his behalf as long as it is slaughtered during the three Days of Tashreeq (11,12, and 13 Dhul-Hijjah).
Therefore, if it is confirmed that that this online organization is aware of these rulings and they are trustworthy, then it is allowed.

Moreover, Sheikh Ja`far At-Talhawi, a prominent Al-Azhar scholar, says:

We fear that there would be some bait and deception from these enterprises. We have heard about many experiences of companies that established their own Web sites and used commerce to attract people to have their own shares in this business. They started gathering and collecting money by tempting their customers with huge and rapid profits. But they only baited them and stole their money.

Unless you have your own methods through which you can make sure of the credibility and honesty of the ones whom you are to delegate to offer sacrifice on your behalf, you should be cautious so as not to be fooled and lied to.

Besides, sacrifice, as well as all the legitimate commandments, should be done so as to be holy. Accordingly, what is important is your confession, not anyone else’s, of the credibility, honesty, and piety of the people who are doing this task. So, you need to look for the person or organization that is credible, honest, pious, and that fears Allah so as to delegate him or it to offer the sacrifice on your behalf.