No big shocker here: Roche has upped its bid for Illumina (Nasdaq: ILMN). With a history of lowball offers followed by raising of bids, it seemed pretty clear the same thing would happen here.

While I'm not surprised Roche increased its offer, the fact that it happened so soon and the magnitude of the increase is a little curious. Roche's first private offer was $40 per share, followed by a $44.50-per-share public offer. Now it's upped the offer all the way to $51 per share, higher than yesterday's close.

Investors smell desperation in the move. They bid up Illumina back above the new offer price, which seems reasonable. Bidding against yourself is generally a losing proposition.

I see the move as a good-faith offer to try to get Illumina to the table. Once the genetic-sequencer maker opens its books, Roche might be willing to make an even higher offer, although another 15% jump might be a little extreme. The current offer is 88% higher than before rumors of the bid became public.

The problem with buying at this level is that the rewards might be fairly minor and the risk is a big unknown. If Roche isn't willing to go much higher and/or Illumina's board isn't willing to negotiate, I could still see Roche walking away from the deal. For sure Illumina is a good fit for Roche, but there are other genetic-sequencing companies out there. Life Technologies (Nasdaq: LIFE), Pacific Biosciences of California (Nasdaq: PACB), and Complete Genomics (Nasdaq: GNOM) could all serve as alternatives for Roche.

The only wild card current investors have is that some white knight that might come in and make a substantially higher offer for Illumina. While that's certainly possible, it seems like a long shot. The other large player in the diagnostics space, Abbott Labs (NYSE: ABT), is working on splitting the company in two, potentially eliminating it from getting into a bidding war.

At this point, buying shares of Illumina is more akin to gambling than investing, since you're at the whim of a couple of executives to determine the final sale price -- or whether there is a sale at all. But it'll be fun to watch the drama unfold from the sidelines, especially now that the most obvious move has already been made.