Spend a few minutes to read this article.
A lot of sites are about matchmaking. A buyer/seller/recruiter/expert/someone wanting to get noticed is looking for the right partner.
Most suffer from the same fatal flaw. Too many of one group are flooding too few of the other group with too many (poor quality) messages. This ruins the experience for everyone (Hello LinkedIn).
The ideas aren’t revolutionary, but are worth refreshing:
1) Limit the number of messages one group can send. This can be done either by absolute numbers (e.g. 50 messages), charging per message, setting a limited number without a response, or limiting messages within a given time period (e.g. 24 hours).
2) Filter messages that are received by one group. Create a filter that removes messages from people with low ratings, where the message has limited content, or where it gets caught in a spam filter.
3) Set a form that must be completed. If most messages are low quality, change the template of the message. Ensure that a user has to complete certain details, provide more information, add links etc…
4) Allow only the minority (in demand) group to send messages. This removes the problem entirely and forces the majority group to optimize their profile as best possible to be noticed.
5) Limit the number of each group who can join. Only allow 1 side of each group to sign up in the first place. Have a waiting list. Until there is a match, don’t allow the user to join.
6) Let users signal when they want to be reached. I receive 30+ emails and LinkedIn messages per week from people offering SEO help. There are times when we will hire consultants to help our clients on their SEO. Sadly most messages are pro-forma, at the wrong time, and (frankly) just terribly written.
You can probably come up with 20 more ideas. The key here is to think about the problem from the perspective of game-theory (or collective action theory).