Feeler (or probe) bets are something I use when the board is draw heavy and I'm out of position with a marginal hand. I think check/folding this situation will get costly over time.

Let's say I'm in early position with pocket 7's and the board is 6,9,10 with two spades. Sure I can bet big and chase out the draws, but almost anything that calls has me beat.

Seems like the better play is to bet 1/4 or 1/3 of the pot. This will surely chase out the total junk hands. Flush and straight draws will still call, but at least you'll know exactly where you stand. Also, anyone with top pair, or two pair on a draw heavy board will almost certainly try to defend their hand by re-raising.

In the above example, if the turn is a straight card or a spade, I can check/fold and only take a minimal loss. If the turn is a blank, then I can feel very confident about betting the car payment.

But in the end, I think it really depends on your reads at the table, and your own table image. It becomes a very vulnerable play once someone catches on to what you're doing.