The way I look at this is simple. Many teams have some form of "arrangement" with paintball kit sponsors but most of the time it just comes down to being a bulk discount, just like you might get at a super market, buy 10 oranges and get 20% off etc. And then if the team in question has even a little bit of sense they will try and reward the company that gave them this deal in some way, e.g. advertising in forums and on jerseys, and publically promoting there products as being good I am sure would also go down well and helps with building relationships(more likely to take big risks with them in the future). But when it comes to the crunch they are not that fussed as they probably still made a profit on it even if it was a small one.
However with sponsorship which I would say is when a company makes some form of loss on the deal, i.e. giving a team free kit or charging below the cost of manufacturer. Then the chances are that the company would want some for of guarantee. Normally in the form of a contract which could include all sorts of clauses, from having to be informed of all others sponsors, having to be informed of other sponsors making counter offers (very common since the Ollie lang incident), and there could also be things like having to use "best endevor" to do certain things such as attend events, perform so many clinics, write so many articles, do so many photo shoots etc etc etc. In this way the sponsor has some form of insurance, so if you break the contract (i.e. publically shooting the wrong brand of marker) then the company can refer back to the contract and demand for example the whole team pay full retail on all gear.
From a company point of view it is a matter of risk and reward. Very low risk giving bulk discount, high risk giving full sets of free kit to a pro team but they might increase the sales of that product to justify it!
Either way the whole conflict of interest does not really happen much as in particular at a higher level sponsors will negiotate what they give and what they expect in return. And at a lower level they are still getting free advertising so who cares.