We're not the only ones who have observed this enticing opportunity. What started with a simple collection of folding chairs, has evolved to a fairly diverse array of cleverly designed seating systems. Some are are differentiated by meaningful features (e.g. seat sling width), while others are silly (e.g. drink holders for wine stems). In addition, there are now large spectator sun umbrellas, portable chair sets that can accomodate an entire team, folding shelters that can protect teams from sun, rain and wind.
I cite spectator gear as an example of a category where companies have quickly responded to observed need-gaps and have introduced innovative and largely sensibly priced products (many featuring lightweight plastics and composite materials) over a relatively short time span. I believe that further innovation opportunities remain within this space. Just watch parents sitting on the sidelines during rainy and cold weather and you'll view the various adaptive behaviors that they (we) currenlty exhibit to cope. Some wear plastic bags as rain ponchos, others use golf umbrellas, some of which are unwieldy (and obstruct others' views). Others still use sleeping bags to cover exposed and chilled legs. These examples alone hint at opportunities for more elegant and effective solutions.
My point is that many categories remain ripe for innovation...both young and even relatively mature ones. The most attractive opportunities will go to those individuals and companies who are savvy enough to recognize need-gaps revealed through observation of adaptive customer behaviors. Are you getting out from behind your desk to learn about your customers' potential needs?