If your brokerage is permitting IDX and VOW datafeeds other brokerages are going to place their contact details beside your listings. Aggregators like Zillow and Trulia are pooling the data from various sources and then selling the responding lead to any agent who will buy those leads.

Brokers are taking back their content; Very eloquent post from San Diego about exactly why.
ARG Announcement

Since we often follow the United States How will this impact our MLS and CREA data sharing?

David Pylyp
Living in Toronto

Well already have Zoocasa here in Canada already which is very similar to these other services. After serveral years trying to get a foothold in the real estate market I really don't see Zoocasa as a significant success or a big threat to the MLS system.

Personally I think that the bigger change / challenge are buyers starting to look at these no commission do it yourself real estate sites. However with their current pricing plan I cannot see how they can remain in business.

I would expect that Trulia & Zillow would have a similar success rate to Zoocasa and would not end up with an MLS feed. On the other hand we know what happend to Zellers when Walmart arrive.