It is really all about appropriate tactics for that particular item..
If the item is not scarce, then it is better to follow the principles that govern most mature snipers - ie don't show your hand, bid your max in the closing seconds.
These are proven sniper tactics and will generally get you the item at a bargain price, certainly lower than if you had joined in a bidding war like so many "newbies" to ebay.
Even if you really want it, like a bus, there should be another along soon.
However it must be said that a "marking" bid to show the seller there is some interest in his item is neither here nor there in terms of forcing the price up - providing if you just bid $1 or a £1 more than the minimum. For good or ill, It does show your hand though.
The main problem is if the item is genuinely rare. In that case I always bid early - it does show my hand, but it also might make some other collectors think twice before engaging in a bidding war. I know this factor does dissuade me from bidding if the converse is true - there are several Korean, German and Swiss collectors who appear to have limitless pockets!
However, generally I think it is a good thing to show interest, as it does put you in a better bargaining position later if the seller does withdraw. It also enables you to approach the seller if the reserve price is not reached. Of the last ten auctions in this category, I have managed to buy seven of the items (in the case of the other three the price asked was unrealistic)