Those who are nervous about renting from a stranger may be more comfortable going through a broker who will escrow a potion of their money, and who will at least ensure they don't lose any money if things go awry with the reservation (the brokers' businesses depend heavily on reputation). No one can absolutely guarantee a
DVC reservation will be there when they arrive - the owner retains the ability to cancel a reservation until check-in has occurred.
There is usually a price premium to go through a broker vs directlythrough an owner. Individual owners may have points available for 11 month bookings that the brokers do not. Lately, it seems the brokers have waitlists for renters who want to book certain resorts before the 7 month window opens. Individual owners may have more friendly cancellation procedures and may be more willing to work with the renter if changes are wanted. It is important to have a contract to make sure all the terms are understood before sending in your money to anyone.
The DIS has had very few reports (I can count on one hand and have fingers left over) of problems when the Disboards.com Rent/Trade Board has been used to bring owners and renters together. That said, it is still important to use common sense and do some checking. The
pinned thread at the top of the Rent/Trade Board provides a very good guide. Keep in mind that while the DIS makes no representations or guarantees of a problem-free transaction, the odds of a successful transaction are very much in your favor if you use the R/T board as recommended in the pinned thread. That's especially true if the poster making the offer has a lot of posts on the DIS - you can get a very good idea of who that person is by reading his/her posts. Those regular posters also love to share their Disney experience with others and care about their DISboards reputation.
I would not be particularly concerned about the lack of replies to a particular offer. (Still need to do your due diligence, of course). As mentioned, many prefer to handle their business via email or telephone rather than PM. Sometimes, resort, price, timing or terms are an issue for prospective renters and the offer sits for awhile before someone responds. Neither would I be particularly concerned about the lack of posts if the poster has purchased one of the Rental Plans available to those who do not have enough post to have the fee waived. (There are still places on the internet where no fees are charged ir minimum number of posts required to post rental offers/requests and IMO, the potential to be scammed is much greater on those sites. YMMV).
My advice is to NEVER do business with someone who contacts you "out of the blue" via PM or email based on a post you made on the DIS. While those contacts may come from honest DVC owners, almost all of the problem transactions that I am aware of have come from transactions that did NOT go through the Rent/Trade Board. Much safer to do business via an offer thread on the R/T Board, than with someone who chooses to ignore / bypass DIS forum rules. If you choose to do business with someone who initially contacted you outside of the R/T forum, be very sure to check them out very carefully before you send money. Remember that if the price is "too good to be true" .............